View source for Efficient energy use

{{Other uses|Energy efficiency (disambiguation)}}
{{Short description|Energy efficiency}}
{{Sustainable energy}}

'''Efficient energy use''', sometimes simply called '''energy efficiency''', is the goal to reduce the amount of energy required to provide products and services. For example, [[building insulation|insulating a home]] allows a building to use less heating and cooling energy to achieve and maintain a comfortable temperature. Installing [[LED lamp|LED lighting]], [[fluorescent lamp|fluorescent lighting]], or natural [[skylight|skylight windows]] reduces the amount of energy required to attain the same level of illumination compared to using traditional [[incandescent light bulb]]s. Improvements in energy efficiency are generally achieved by adopting a more efficient technology or production process<ref>[[Mark Diesendorf|Diesendorf, Mark]] (2007). ''[[Greenhouse Solutions with Sustainable Energy]]'', UNSW Press, p. 86.</ref> or by application of commonly accepted methods to reduce energy losses.

There are many motivations to improve energy efficiency. Reducing energy use reduces energy costs and may result in a financial cost saving to consumers if the energy savings offset any additional costs of implementing an energy-efficient technology. Reducing energy use is also seen as a solution to the problem of reducing [[greenhouse gas]] emissions. According to the [[International Energy Agency]], improved [[energy-efficient buildings|energy efficiency in buildings]], industrial processes and [[sustainable transportation|transportation]] could reduce the world's energy needs in 2050 by one third, and help control global emissions of greenhouse gases.<ref>{{cite web|author=Sophie Hebden |url=http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=2929&language=1 |title=Invest in clean technology says IEA report |publisher=Scidev.net |date=2006-06-22 |accessdate=2010-07-16}}</ref> Another important solution is to remove government-led energy subsidies that promote high energy consumption and inefficient energy use in more than half of the countries in the world.<ref>{{cite journal|author=Indra Overland |date=2010|title=Subsidies for Fossil Fuels and Climate Change: A Comparative Perspective|journal=International Journal of Environmental Studies|volume=67|pages=203–217|url=https://www.researchgate.net/publication/240515305}}</ref>

Energy efficiency and [[renewable energy]] are said to be the ''twin pillars'' of [[sustainable energy]] policy<ref>{{cite book |last1= Prindle |first1= Bill |last2= Eldridge |first2= Maggie |last3= Eckhardt |first3= Mike |last4= Frederick |first4= Alyssa |title= The twin pillars of sustainable energy: synergies between energy efficiency and renewable energy technology and policy |date= May 2007 |publisher= American Council for an Energy-Efficient Economy (ACEEE) |place= Washington, DC, USA |url= http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.545.4606&rep=rep1&type=pdf |access-date= 2016-04-03}}</ref> and are high priorities in the sustainable [[energy hierarchy]]. In many countries energy efficiency is also seen to have a national security benefit because it can be used to reduce the level of energy imports from foreign countries and may slow down the rate of energy at which domestic energy resources are depleted.

==Overview==
{{Further|Domestic energy consumption}}
Energy efficiency has proved to be a cost-effective strategy for building economies without necessarily increasing [[energy consumption]]. For example, the state of [[California]] began implementing energy-efficiency measures in the mid-1970s, including building code and appliance standards with strict efficiency requirements. During the following years, California's energy consumption has remained approximately flat on a per capita basis while national US consumption doubled.<ref>{{cite book|last=Zehner|first=Ozzie|title=Green Illusions|year=2012|publisher=UNP|location=London|pages=180–181|url=http://greenillusions.org}}</ref> As part of its strategy, California implemented a "loading order" for new energy resources that puts energy efficiency first, renewable electricity supplies second, and new fossil-fired power plants last.<ref>{{cite web|url=http://www.energy.ca.gov/2005publications/CEC-400-2005-043/CEC-400-2005-043.PDF |title=Loading Order White Paper |format=PDF |accessdate=2010-07-16}}</ref> States such as Connecticut and New York have created quasi-public [[Green bank (financial institution)|Green Banks]] to help residential and commercial building-owners finance energy efficiency upgrades that reduce emissions and cut consumers' energy costs.<ref>{{cite web|author=Kennan, Hallie|url=http://energyinnovation.org/wp-content/uploads/2014/06/WorkingPaper_StateGreenBanks.pdf|format=PDF|title=WORKING PAPER: STATE GREEN BANKS FOR CLEAN ENERGY|website=Energyinnovation.org|accessdate=26 March 2019}}</ref>

Lovin's [[Rocky Mountain Institute]] points out that in industrial settings, "there are abundant opportunities to save 70% to 90% of the energy and cost for lighting, fan, and pump systems; 50% for electric motors; and 60% in areas such as heating, cooling, office equipment, and appliances." In general, up to 75% of the electricity used in the US today could be saved with efficiency measures that cost less than the electricity itself, the same holds true for home settings. The US Department of Energy has stated that there is potential for energy saving in the magnitude of 90 Billion kWh by increasing home energy efficiency.<ref>{{cite web |url=http://www.greencollaroperations.com/weatherization-austin-tx.html |title=Weatherization in Austin, Texas |publisher=Green Collar Operations |accessdate=2010-07-16 |url-status=dead |archiveurl=https://web.archive.org/web/20090803235602/http://www.greencollaroperations.com/weatherization-austin-tx.html |archivedate=2009-08-03 }}</ref>

Other studies have emphasized this. A report published in 2006 by the [[McKinsey Global Institute]], asserted that "there are sufficient economically viable opportunities for energy-productivity improvements that could keep global energy-demand growth at less than 1 percent per annum"—less than half of the 2.2 percent average growth anticipated through 2020 in a business-as-usual scenario.<ref name= NYT292006>{{cite news|title= Energy Use Can Be Cut by Efficiency, Survey Says.... |url= https://www.nytimes.com/2006/11/29/business/29energy.html |accessdate= November 29, 2006|newspaper=The New York Times |date= November 29, 2006|author= Steve Lohr}}</ref> Energy productivity, which measures the output and quality of goods and services per unit of energy input, can come from either reducing the amount of energy required to produce something, or from increasing the quantity or quality of goods and services from the same amount of energy.

The [[Vienna Climate Change Talks 2007]] Report, under the auspices of the [[United Nations Framework Convention on Climate Change]] (UNFCCC), clearly shows "that energy efficiency can achieve real emission reductions at low cost."<ref>{{cite web|url=http://unfccc.int/files/press/news_room/press_releases_and_advisories/application/pdf/20070831_vienna_closing_press_release.pdf|format=PDF|title=PRESS RELEASE : Vienna UN conference shows consensus on key building blocks for effective international response to climate change|website=Unfccc.int|accessdate=26 March 2019}}</ref>

[[International standard]]s ISO{{nbsp}}17743 and ISO{{nbsp}}17742 provide a documented methodology for calculating and reporting on energy savings and energy efficiency for countries and cities.<ref name="iso-17743">
{{cite book
| title= ISO 17743:2016 - Energy savings — Definition of a methodological framework applicable to calculation and reporting on energy savings
| work= International Standards Association (ISO)
| location= Geneva, Switzerland
| url= http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=60376
| access-date= 2016-11-11
}}
</ref><ref name="iso-17742">
{{cite book
| title= ISO 17742:2015 — Energy efficiency and savings calculation for countries, regions and cities
| work= International Standards Association (ISO)
| location= Geneva, Switzerland
| url= http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=60374
| access-date= 2016-11-11
}}
</ref>

==Benefits==
From the point of view of an energy consumer, the main motivation of energy efficiency is often simply saving money by lowering the cost of purchasing energy. Additionally, from an energy policy point of view, there has been a long trend in a wider recognition of energy efficiency as the "first fuel", meaning the ability to replace or avoid the consumption of actual fuels. In fact, [[International Energy Agency]] has calculated that the application of energy efficiency measures in the years 1974-2010 has succeeded in avoiding more energy consumption in its member states than is the consumption of any particular fuel, including oil, coal and natural gas.<ref name="Benefits">[[International Energy Agency]]: [https://www.iea.org/publications/freepublications/publication/Multiple_Benefits_of_Energy_Efficiency.pdf Capturing the Multiple Benefits of Energy Efficiency]. OECD, Paris, 2014.</ref>

Moreover, it has long been recognized that energy efficiency brings other benefits additional to the reduction of energy consumption.<ref>Weinsziehr, T.; Skumatz, L. Evidence for Multiple Benefits or NEBs: Review on Progress and Gaps from the IEA Data and Measurement Subcommittee. In Proceedings of the International Energy Policy & Programme Evaluation Conference, Amsterdam, The Netherlands, 7–9 June 2016.</ref> Some estimates of the value of these other benefits, often called multiple benefits, co-benefits, ancillary benefits or non-energy benefits, have put their summed value even higher than that of the direct energy benefits.<ref>Ürge-Vorsatz, D.; Novikova, A.; Sharmina, M. Counting good: Quantifying the co-benefits of improved efficiency in buildings. In Proceedings of the ECEEE 2009 Summer Study, Stockholm, Sweden, 1–6 June 2009.</ref> These multiple benefits of energy efficiency include things such as reduced climate change impact, reduced air pollution and improved health, improved indoor conditions, improved energy security and reduction of the price risk for energy consumers. Methods for calculating the monetary value of these multiple benefits have been developed, including e.g. the choice experiment method for improvements that have a subjective component (such as aesthetics or comfort)<ref name="Benefits"/> and Tuominen-Seppänen method for price risk reduction.<ref>B Baatz, J Barrett, B Stickles: [https://aceee.org/research-report/u1803 Estimating the Value of Energy Efficiency to Reduce Wholesale Energy Price Volatility]. [[ACEEE]], Washington D.C., 2018.</ref> When included in the analysis, the economic benefit of energy efficiency investments can be shown to be significantly higher than simply the value of the saved energy.<ref name="Benefits"/>

==Appliances==
{{See also|green computing|solar lamp|energy saving lamp|power usage effectiveness}}

Modern appliances, such as, [[freezers]], [[oven]]s, [[stove]]s, [[dishwasher]]s, and clothes washers and dryers, use significantly less energy than older appliances. Installing a clothesline will significantly reduce one's energy consumption as their dryer will be used less. Current energy-efficient refrigerators, for example, use 40 percent less energy than conventional models did in 2001. Following this, if all households in Europe changed their more than ten-year-old appliances into new ones, 20 billion kWh of electricity would be saved annually, hence reducing CO<sub>2</sub> emissions by almost 18 billion kg.<ref>{{cite web |url=http://ecosavings.electrolux.com/#int_en |title=Ecosavings |publisher=Electrolux.com |accessdate=2010-07-16 |url-status=dead |archiveurl=https://web.archive.org/web/20110806070945/http://ecosavings.electrolux.com/#int_en |archivedate=2011-08-06 }}</ref> In the US, the corresponding figures would be 17 billion kWh of electricity and {{convert|27000000000|lb|kg|abbr=on}} CO<sub>2</sub>.<ref>{{cite web |url=http://www.electrolux.com/ecosavings_us |title=Ecosavings (Tm) Calculator |publisher=Electrolux.com |accessdate=2010-07-16 |archive-url=https://web.archive.org/web/20100818193713/http://www.electrolux.com/EcoSavings%5FUS/ |archive-date=2010-08-18 |url-status=dead }}</ref> According to a 2009 study from [[McKinsey & Company]] the replacement of old appliances is one of the most efficient global measures to reduce emissions of greenhouse gases.<ref>{{cite journal|journal=McKinsey Global Institute|title=Pathways to a Low-Carbon Economy: Version 2 of the Global Greenhouse Gas Abatement Cost Curve|url=http://www.mckinsey.com/~/media/mckinsey/dotcom/client_service/sustainability/cost%20curve%20pdfs/pathways_lowcarbon_economy_version2.ashx|accessdate=February 16, 2016|page=7|date=2009}}</ref> Modern power management systems also reduce energy usage by idle appliances by turning them off or putting them into a low-energy mode after a certain time. Many countries identify energy-efficient appliances using [[energy input labeling]].<ref name=app>{{cite web|author=Environmental and Energy Study Institute |url=http://www.eesi.org/buildings_efficiency_0506 |title=Energy-Efficient Buildings: Using whole building design to reduce energy consumption in homes and offices |publisher=Eesi.org |accessdate=2010-07-16}}</ref>

The impact of energy efficiency on peak demand depends on when the appliance is used. For example, an air conditioner uses more energy during the afternoon when it is hot. Therefore, an energy-efficient air conditioner will have a larger impact on peak demand than off-peak demand. An energy-efficient dishwasher, on the other hand, uses more energy during the late evening when people do their dishes. This appliance may have little to no impact on peak demand.

==Building design==
{{See also|Building performance|Energy-efficient landscaping|Window insulation film|Phase-out of incandescent light bulbs}}[[File:Empire State Building from the Top of the Rock.jpg|thumb|Receiving a Gold rating for energy and environmental design in September 2011, the [[Empire State Building]] is the tallest and largest LEED certified building in the United States and Western Hemisphere.,<ref name="inhabitat1">{{cite web|url=http://inhabitat.com/nyc/empire-state-building-achieves-leed-gold-certification/ |title=Empire State Building Achieves LEED Gold Certification &#124; Inhabitat New York City|publisher=Inhabitat.com |accessdate=October 12, 2011}}</ref> though it will likely be overtaken by New York's own [[One World Trade Center]].<ref name="1wtcLEED">{{cite web|url=http://plus.usgbc.org/f2-reaching-new-heights/ |title=Declared the tallest building in the US — One World Trade Center is on track for LEED. |publisher=[[United States Green Building Council]]|author=Alison Gregor |accessdate=December 12, 2015}}</ref>]]

Buildings are an important field for energy efficiency improvements around the world because of their role as a major energy consumer. However, the question of energy use in buildings is not straightforward as the indoor conditions that can be achieved with energy use vary a lot. The measures that keep buildings comfortable, lighting, heating, cooling and ventilation, all consume energy. Typically the level of energy efficiency in a building is measured by dividing energy consumed with the floor area of the building which is referred to as specific energy consumption (SEC) or energy use intensity (EUI):<ref>{{cite web|url=https://www.energystar.gov/buildings|title=ENERGY STAR Buildings and Plants|website=Energystar.gov|accessdate=26 March 2019}}</ref>
:<math>\frac \text{Energy consumed}\text{Built area}</math>

However, the issue is more complex as building materials have [[embodied energy]] in them. On the other hand, energy can be recovered from the materials when the building is dismantled by reusing materials or burning them for energy. Moreover, when the building is used, the indoor conditions can vary resulting in higher and lower quality indoor environments. Finally, overall efficiency is affected by the use of the building: is the building occupied most of the time and are spaces efficiently used — or is the building largely empty? It has even been suggested that for a more complete accounting of energy efficiency, SEC should be amended to include these factors:<ref>Juha Forsström, Pekka Lahti, Esa Pursiheimo, Miika Rämä, Jari Shemeikka, Kari Sipilä, Pekka Tuominen & Irmeli Wahlgren (2011): [http://www.vtt.fi/inf/pdf/tiedotteet/2011/T2581.pdf Measuring energy efficiency]. VTT Technical Research Centre of Finland.</ref>
:<math>\frac {\text{Embodied energy} + \text{Energy consumed} - \text{Energy recovered}}{\text{Built area} \times \text{Utilization rate} \times \text{Quality factor}}</math>

Thus a balanced approach to energy efficiency in buildings should be more comprehensive than simply trying to minimize energy consumed. Issues such as quality of indoor environment and efficiency of space use should be factored in. Thus the measures used to improve energy efficiency can take many different forms. Often they include passive measures that inherently reduce the need to use energy, such as better insulation. Many serve various functions improving the indoor conditions as well as reducing energy use, such as increased use of natural light.

A building's location and surroundings play a key role in regulating its temperature and illumination. For example, trees, landscaping, and hills can provide shade and block wind. In cooler climates, designing northern hemisphere buildings with south facing windows and southern hemisphere buildings with north facing windows increases the amount of sun (ultimately heat energy) entering the building, minimizing energy use, by maximizing [[passive solar heating]]. Tight building design, including energy-efficient windows, well-sealed doors, and additional thermal insulation of walls, basement slabs, and foundations can reduce heat loss by 25 to 50 percent.<ref name=app/><ref>Most heat is lost through the walls of your building, in fact about a third of all heat losses occur in this area. [https://www.simplybusinessenergy.co.uk/news/electricity-and-energy-cost-savings-for-small-businesses~188/ Simply Business Energy] {{Webarchive|url=https://web.archive.org/web/20160604161505/https://www.simplybusinessenergy.co.uk/news/electricity-and-energy-cost-savings-for-small-businesses~188/ |date=2016-06-04 }}</ref>

Dark roofs may become up to 39&nbsp;°C (70&nbsp;°F) hotter than the most [[reflective surfaces (climate engineering)|reflective white surfaces]]. They transmit some of this additional heat inside the building. US Studies have shown that lightly colored roofs use 40 percent less energy for cooling than buildings with darker roofs. White roof systems save more energy in sunnier climates. Advanced electronic heating and cooling systems can moderate energy consumption and improve the comfort of people in the building.<ref name=app/>

Proper placement of windows and skylights as well as the use of architectural features that reflect light into a building can reduce the need for artificial lighting. Increased use of natural and task lighting has been shown by one study to increase productivity in schools and offices.<ref name=app/> [[Compact fluorescent lamp]]s use two-thirds less energy and may last 6 to 10 times longer than [[incandescent light bulb]]s. Newer fluorescent lights produce a natural light, and in most applications they are cost effective, despite their higher initial cost, with payback periods as low as a few months. [[LED lamp]]s use only about 10% of the energy an incandescent lamp requires.

Effective energy-efficient building design can include the use of low cost Passive Infra Reds (PIRs) to switch-off lighting when areas are unnoccupied such as toilets, corridors or even office areas out-of-hours. In addition, lux levels can be monitored using daylight sensors linked to the building's lighting scheme to switch on/off or dim the lighting to pre-defined levels to take into account the natural light and thus reduce consumption. Building Management Systems (BMS) link all of this together in one centralised computer to control the whole building's lighting and power requirements.<ref>Creating Energy Efficient Offices - Electrical Contractor Fit-out Article</ref>

In an analysis that integrates a residential bottom-up simulation with an economic multi-sector model, it has been shown that variable heat gains caused by insulation and air-conditioning efficiency can have load-shifting effects that are not uniform on the electricity load. The study also highlighted the impact of higher household efficiency on the power generation capacity choices that are made by the power sector.<ref>{{cite journal |doi=10.1007/s12053-015-9392-9 |title=Beyond the end-consumer: how would improvements in residential energy efficiency affect the power sector in Saudi Arabia? |year=2015 |last1=Matar |first1=W |journal=Energy Efficiency}}</ref>

The choice of which space heating or cooling technology to use in buildings can have a significant impact on energy use and efficiency. For example, replacing an older 50% efficient [[furnace#Household furnaces|natural gas furnace]] with a new 95% efficient one will dramatically reduce energy use, carbon emissions, and winter natural gas bills. [[Ground source heat pump]]s can be even more energy-efficient and cost-effective. These systems use pumps and compressors to move refrigerant fluid around a thermodynamic cycle in order to "pump" heat against its natural flow from hot to cold, for the purpose of transferring heat into a building from the large thermal reservoir contained within the nearby ground. The end result is that heat pumps typically use four times less electrical energy to deliver an equivalent amount of heat than a direct electrical heater does. Another advantage of a ground source heat pump is that it can be reversed in summertime and operate to cool the air by transferring heat from the building to the ground. The disadvantage of ground source heat pumps is their high initial capital cost, but this is typically recouped within five to ten years as a result of lower energy use.

[[Smart meter]]s are slowly being adopted by the commercial sector to highlight to staff and for internal monitoring purposes the building's energy usage in a dynamic presentable format. The use of Power Quality Analysers can be introduced into an existing building to assess usage, harmonic distortion, peaks, swells and interruptions amongst others to ultimately make the building more energy-efficient. Often such meters communicate by using [[wireless sensor network]]s.

[[Green Building XML]] (gbXML) is an emerging schema, a subset of the [[Building Information Modeling]] efforts, focused on green building design and operation. gbXML is used as input in several energy simulation engines. But with the development of modern computer technology, a large number of [[building performance simulation]] tools are available on the market. When choosing which simulation tool to use in a project, the user must consider the tool's accuracy and reliability, considering the building information they have at hand, which will serve as input for the tool. Yezioro, Dong and Leite<ref>{{cite journal |doi=10.1016/j.enbuild.2007.04.014 |title=An applied artificial intelligence approach towards assessing building performance simulation tools |year=2008 |last1=Yezioro |first1=A |last2=Dong |first2=B |last3=Leite |first3=F |journal=Energy and Buildings |volume=40 |issue=4 |page=612}}</ref> developed an artificial intelligence approach towards assessing building performance simulation results and found that more detailed simulation tools have the best simulation performance in terms of heating and cooling electricity consumption within 3% of mean absolute error.

[[Leadership in Energy and Environmental Design]] (LEED) is a rating system organized by the [[US Green Building Council]] (USGBC) to promote environmental responsibility in building design. They currently offer four levels of certification for existing buildings (LEED-EBOM) and new construction (LEED-NC) based on a building's compliance with the following criteria: [[Sustainable sites]], [[water efficiency]], energy and atmosphere, materials and resources, indoor environmental quality, and innovation in design.<ref>{{cite web |title=LEED v4 for Building Design and Construction Checklist |url=http://www.usgbc.org/sites/default/files/LEED%20v4%20for%20Building%20Design%20and%20Construction%20_1%20PAGE_0.xlsx |archive-url=https://wayback.archive-it.org/all/20150226000022/http://www.usgbc.org/sites/default/files/LEED%20v4%20for%20Building%20Design%20and%20Construction%20_1%20PAGE_0.xlsx |url-status=dead |archive-date=26 February 2015 |website=USGBC |accessdate=29 April 2015 }}</ref> In 2013, USGBC developed the LEED Dynamic Plaque, a tool to track building performance against LEED metrics and a potential path to recertification. The following year, the council collaborated with [[Honeywell]] to pull data on energy and water use, as well as indoor air quality from a BAS to automatically update the plaque, providing a near-real-time view of performance. The USGBC office in [[Washington, D.C.]] is one of the first buildings to feature the live-updating LEED Dynamic Plaque.<ref>{{cite web|title=Honeywell, USGBC Tool Monitors Building Sustainability|url=http://www.environmentalleader.com/2014/10/22/honeywell-usgbc-tool-monitors-building-sustainability/|website=Environmental Leader|accessdate=29 April 2015|archive-url=https://web.archive.org/web/20150713010208/http://www.environmentalleader.com/2014/10/22/honeywell-usgbc-tool-monitors-building-sustainability/|archive-date=13 July 2015|url-status=dead}}</ref>

A [[deep energy retrofit]] is a whole-building analysis and construction process that uses to achieve much larger energy savings than conventional [[green retrofit|energy retrofits]]. Deep energy retrofits can be applied to both residential and non-residential (“commercial”) buildings. A deep energy retrofit typically results in energy savings of 30 percent or more, perhaps spread over several years, and may significantly improve the building value.<ref>{{Cite web |url=http://jeancarassus.zumablog.com/images/2128_uploads/Fuerst_New_paper.pdf |title=Archived copy |access-date=2013-08-21 |archive-url=https://web.archive.org/web/20120611071236/http://jeancarassus.zumablog.com/images/2128_uploads/Fuerst_New_paper.pdf |archive-date=2012-06-11 |url-status=dead }}</ref> The [[Empire State Building]] has undergone a deep energy retrofit process that was completed in 2013. The project team, consisting of representatives from [[Johnson Controls]], [[Rocky Mountain Institute]], [[Clinton Climate Initiative]], and [[Jones Lang LaSalle]] will have achieved an annual energy use reduction of 38% and $4.4 million.<ref name=ESB>{{cite web|url=http://esbnyc.com/sustainability_energy_efficiency.asp |title=Visit > Sustainability & Energy Efficiency &#124; Empire State Building |publisher=Esbnyc.com |date=2011-06-16 |accessdate=2013-08-21}}</ref> For example, the 6,500 windows were remanufactured onsite into [[superwindow]]s which block heat but pass light. [[Air conditioning]] operating costs on hot days were reduced and this saved $17 million of the project's capital cost immediately, partly funding other retrofitting.<ref>{{cite web |url=http://www.foreignaffairs.com/articles/137246/amory-b-lovins/a-farewell-to-fossil-fuels |title=A Farewell to Fossil Fuels |author=Amory Lovins |date=March–April 2012 |work=Foreign Affairs}}</ref> Receiving a gold [[Leadership in Energy and Environmental Design|Leadership in Energy and Environmental Design (LEED)]] rating in September 2011, the Empire State Building is the tallest LEED certified building in the United States.<ref name="inhabitat1"/>
The [[Indianapolis City-County Building]] recently underwent a deep energy retrofit process, which has achieved an annual energy reduction of 46% and $750,000 annual energy saving.

Energy retrofits, including deep, and other types undertaken in residential, commercial or industrial locations are generally supported through various forms of financing or incentives. Incentives include pre-packaged rebates where the buyer/user may not even be aware that the item being used has been rebated or "bought down". "Upstream" or "Midstream" buy downs are common for efficient lighting products. Other rebates are more explicit and transparent to the end user through the use of formal applications. In addition to rebates, which may be offered through government or utility programs, governments sometimes offer tax incentives for energy efficiency projects. Some entities offer rebate and payment guidance and facilitation services that enable energy end use customers tap into rebate and incentive programs.

To evaluate the economic soundness of energy efficiency investments in buildings, [[cost-effectiveness analysis]] or CEA can be used. A CEA calculation will produce the value of energy saved, sometimes called ''[[negawatt]]s'', in $/kWh. The energy in such a calculation is virtual in the sense that it was never consumed but rather saved due to some energy efficiency investment being made. Thus CEA allows comparing the price of negawatts with price of energy such as electricity from the grid or the cheapest renewable alternative. The benefit of the CEA approach in energy systems is that it avoids the need to guess future energy prices for the purposes of the calculation, thus removing the major source of uncertainty in the appraisal of energy efficiency investments.<ref>Pekka Tuominen, Francesco Reda, Waled Dawoud, Bahaa Elboshy, Ghada Elshafei, Abdelazim Negm: [http://doi.org/10.1016/S2212-5671(15)00195-1 Economic Appraisal of Energy Efficiency in Buildings Using Cost-effectiveness Assessment]. Procedia Economics and Finance, Volume 21, 2015, Pages 422–430.</ref>

==Energy efficiency by country==

===Europe===
{{See also|Energy efficiency in Europe (study)}}
{{Expand section|proper text and additional citations|date=June 2016}}

Energy efficiency targets for 2020 and 2030.

The first EU-wide energy efficiency target was set in 1998. Member states agreed to improve energy efficiency by 1 percent a year over twelve years. In addition, legislation about products, industry, transport and buildings has contributed to a general energy efficiency framework. More effort is needed to address heating and cooling: there is more heat wasted during electricity production in Europe than is required to heat all buildings in the continent.<ref>{{Cite web|url=http://www.heatroadmap.eu/|title=Heat Roadmap Europe|website=Heatroadmap.eu|access-date=2018-04-24}}</ref> All in all, EU energy efficiency legislation is estimated to deliver savings worth the equivalent of up to 326 million tons of oil per year by 2020.<ref name="auto">{{Cite news|url=https://www.boell.de/en/2018/04/24/energy-atlas-2018-figures-and-facts-about-renewables-europe?dimension1=ds_energyatlas|title=Energy Atlas 2018: Figures and Facts about Renewables in Europe {{!}} Heinrich Böll Foundation|work=Heinrich Böll Foundation|access-date=2018-04-24|language=en}}</ref>

The EU set itself a [[EU Energy Efficiency Directive 2012|20% energy savings target]] by 2020 compared to 1990 levels, but member states decide individually how energy savings will be achieved. At an EU summit in October 2014, EU countries agreed on a new energy efficiency target of 27% or greater by 2030. One mechanism used to achieve the target of 27% is the 'Suppliers Obligations & White Certificates'.<ref>{{cite web|title=Suppliers Obligations & White Certificates|url=http://iet.jrc.ec.europa.eu/energyefficiency/white-certificates|website=Europa.EU|publisher=Europa.eu|accessdate=2016-07-07}}</ref> The ongoing debate around the 2016 Clean Energy Package also puts an emphasis on energy efficiency, but the goal will probably remain around 30% greater efficiency compared to 1990 levels.<ref name="auto"/> Some have argued that this will not be enough for the EU to meet its Paris Agreement goals of reducing greenhouse gas emissions by 40% compared to 1990 levels.

===Australia===
The [[Australian national government]] is actively leading the country in efforts to increase their energy efficiency, mainly through the government's [[Department of Industry and Science]]. In July 2009, the [[Council of Australian Governments]], which represents the individual states and territories of Australia, agreed to a National Strategy on Energy Efficiency (NSEE).<ref>{{citation |title=National Strategy on Energy Efficiency |publisher=Industry.gov.au |date=16 August 2015 |url=http://industry.gov.au/Energy/EnergyEfficiency/Pages/NationalStrategyEnergyEfficiency.aspx |url-status=dead |archiveurl=https://web.archive.org/web/20150913191712/http://www.industry.gov.au/Energy/EnergyEfficiency/Pages/NationalStrategyEnergyEfficiency.aspx |archivedate=13 September 2015 }}</ref>

This is a ten-year plan accelerate the implementation of a nationwide adoption of energy-efficient practices and a preparation for the country's transformation into a [[low carbon]] future. There are several different areas of energy use addressed within the NSEE. But, the chapter devoted to the approach on energy efficiency that is to be adopted on a national level stresses four points in achieving stated levels of energy efficiency. They are:
*To help households and businesses transition to a low carbon future
*To streamline the adoption of efficient energy
*To make buildings more energy-efficient
*For governments to work in partnership and lead the way to energy efficiency

The overriding agreement that governs this strategy is the National Partnership Agreement on Energy Efficiency.<ref>{{citation|title=National Partnership Agreement on Energy Efficiency |publisher=Fif.gov.au |date=16 August 2015 |url=http://www.federalfinancialrelations.gov.au/content/npa/environment/energy_efficiency/national_partnership.pdf |url-status=dead |archiveurl=https://web.archive.org/web/20150312005515/http://federalfinancialrelations.gov.au/content/npa/environment/energy_efficiency/national_partnership.pdf |archivedate=2015-03-12 }}</ref>

This document also explains the role of both the [[commonwealth]] and the individual states and territories in the NSEE, as well provides for the creation of benchmarks and measurement devices which will transparently show the nation's progress in relation to the stated goals, and addresses the need for funding of the strategy in order to enable it to move forward.

===Canada===

In August 2017, the Government of Canada released [https://www.nrcan.gc.ca/sites/www.nrcan.gc.ca/files/emmc/pdf/Building_Smart_en.pdf Build Smart - Canada's Buildings Strategy], as a key driver of the [https://www.canada.ca/en/services/environment/weather/climatechange/pan-canadian-framework.html Pan Canadian Framework on Clean Growth and Climate Change], Canada's national climate strategy.

The Build Smart strategy seeks to dramatically increase the energy-efficiency performance of existing and new Canadian buildings, and establishes five goals to that end:
*Federal, provincial, and territorial governments will work to develop and adopt increasingly stringent model building codes, starting in 2020, with the goal that provinces and territories adopt a “[[Zero-energy building|net-zero energy]] ready” model building code by 2030.
*Federal, provincial, and territorial governments will work to develop a model code for existing buildings by 2022, with the goal that provinces and territories adopt the code.
*Federal, provincial, and territorial governments will work together with the aim of requiring labelling of building energy use by as early as 2019.
*The federal government will set new standards for heating equipment and other key technologies to the highest level of efficiency that is economically and technically achievable.
*Provincial and territorial governments will work to sustain and expand efforts to retrofit existing buildings by supporting energy efficiency improvements and by accelerating the adoption of high-efficiency equipment while tailoring their programs to regional circumstances.

The strategy details a range of activities the Government of Canada will pursue, and investments it will make, in support of the goals. As of early 2018, only one of Canada's 10 provinces and three territories, British Columbia, has developed a policy in support of federal government's goal to reach net zero energy ready ambitions: the [[BC Energy Step Code]].

Local British Columbia governments may use the BC Energy Step Code, if they wish, to incentivize or require a level of energy efficiency in new construction that goes above and beyond the requirements of the base building code. The regulation and standard is designed as a technical roadmap to help the province reach its target that all new buildings will attain a net zero energy ready level of performance by 2032.

===Germany===
{{See also|German National Action Plan on Energy Efficiency}}

Energy efficiency is central to [[energy policy]] in [[Germany]].<ref name="bmwi-2010">
{{cite book
|author1= Federal Ministry of Economics and Technology (BMWi)
|author2= Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU)
|title= Energy concept for an environmentally sound, reliable and affordable energy supply
|date= 28 September 2010
|publisher= Federal Ministry of Economics and Technology (BMWi)
|place= Berlin, Germany
|url= http://www.bmwi.de/English/Redaktion/Pdf/energy-concept,property=pdf,bereich=bmwi,sprache=en,rwb=true.pdf
|access-date= 2016-05-01
|url-status= dead
|archiveurl= https://web.archive.org/web/20161006040920/http://www.bmwi.de/English/Redaktion/Pdf/energy-concept%2Cproperty%3Dpdf%2Cbereich%3Dbmwi%2Csprache%3Den%2Crwb%3Dtrue.pdf
|archivedate= 6 October 2016
}}</ref>
As of late 2015, national policy includes the following efficiency and consumption targets (with actual values for 2014):<ref name="bmwi-2015-b">
{{cite book
|title= The Energy of the Future: Fourth "Energy Transition" Monitoring Report — Summary
|date= November 2015
|publisher= Federal Ministry for Economic Affairs and Energy (BMWi)
|place= Berlin, Germany
|url= https://www.bmwi.de/BMWi/Redaktion/PDF/V/vierter-monitoring-bericht-energie-der-zukunft-englische-kurzfassung,property=pdf,bereich=bmwi2012,sprache=de,rwb=true.pdf
|access-date= 2016-06-09
|url-status= dead
|archiveurl= https://web.archive.org/web/20160920202129/https://www.bmwi.de/BMWi/Redaktion/PDF/V/vierter-monitoring-bericht-energie-der-zukunft-englische-kurzfassung%2Cproperty%3Dpdf%2Cbereich%3Dbmwi2012%2Csprache%3Dde%2Crwb%3Dtrue.pdf
|archivedate= 2016-09-20
}}</ref>{{rp|4}}

{| class="wikitable" {{ts|ar}}
! Efficiency and consumption target !! 2014 !! 2020 !! 2050
|-
| Primary energy consumption (base year 2008)
| −8.7% || −20% || −50%
|- style="vertical-align: top"
| Final energy productivity (2008–2050)
| 1.6%/year<br />(2008–2014) || colspan= 2 |2.1%/year<br />(2008–2050)
|-
| Gross electricity consumption (base year 2008)
| −4.6% || −10% || −25%
|-
| Primary energy consumption in buildings (base year 2008)
| −14.8% || || −80%
|-
| Heat consumption in buildings (base year 2008)
| −12.4% || −20% ||
|-
| Final energy consumption in transport (base year 2005)
| 1.7% || −10% || −40%
|}

Recent progress toward improved efficiency has been steady aside from the [[financial crisis of 2007–08]].<ref>
{{cite book
| last1= Schlomann |first1= Barbara
| last2= Eichhammer |first2= Wolfgang
| title= Energy efficiency policies and measures in Germany
| year= 2012
| publisher= Fraunhofer Institute for Systems and Innovation Research ISI
| place= Karlsruhe, Germany
| url= http://www.isi.fraunhofer.de/isi-wAssets/docs/x/de/publikationen/National-Report_Germany_November-2012.pdf
| access-date= 2016-05-01
}}</ref>
Some however believe energy efficiency is still under-recognised in terms of its contribution to Germany's energy transformation (or ''[[Energiewende]]'').<ref>{{cite book
| author= Agora Energiewende
| title= Benefits of energy efficiency on the German power sector: summary of key findings from a study conducted by Prognos AG and IAEW
| year= 2014
| publisher= [[Agora Energiewende]]
| place= Berlin, Germany
| url= http://www.agora-energiewende.de/fileadmin/Projekte/2012/positive-effekte-energieeffizienz/Agora_ECF_RAP_System_Benefit_Study_short_version_web.pdf
| access-date= 2016-04-29
| archive-url= https://web.archive.org/web/20160602080036/https://www.agora-energiewende.de/fileadmin/Projekte/2012/positive-effekte-energieeffizienz/Agora_ECF_RAP_System_Benefit_Study_short_version_web.pdf
| archive-date= 2016-06-02
| url-status= dead
}}</ref>

Efforts to reduce final energy consumption in transport sector have not been successful, with a growth of 1.7% between 2005–2014. This growth is due to both road passenger and road freight transport. Both sectors increased their overall distance travelled to record the highest figures ever for Germany. Rebound effects played a significant role, both between improved vehicle efficiency and the distance travelled, and between improved vehicle efficiency and an increase in vehicle weights and engine power.<ref name="loeschel-etal-2015">
{{cite book
|first1= Andreas
|last1= Löschel
|first2= Georg
|last2= Erdmann
|first3= Frithjof
|last3= Staiß
|first4= Hans-Joachim
|last4= Ziesing
|title= Statement on the Fourth Monitoring Report of the Federal Government for 2014
|date= November 2015
|publisher= Expert Commission on the "Energy of the Future" Monitoring Process
|place= Germany
|url= https://www.bmwi.de/BMWi/Redaktion/PDF/V/vierter-monitoringbericht-energie-der-zukunft-stellungnahme-zusammenfassung-englisch,property=pdf,bereich=bmwi2012,sprache=de,rwb=true.pdf
|access-date= 2016-06-09
|url-status= dead
|archiveurl= https://web.archive.org/web/20160805164825/http://www.bmwi.de/BMWi/Redaktion/PDF/V/vierter-monitoringbericht-energie-der-zukunft-stellungnahme-zusammenfassung-englisch,property=pdf,bereich=bmwi2012,sprache=de,rwb=true.pdf
|archivedate= 2016-08-05
}}</ref>{{rp|12}}

On 3 December 2014, the German federal government released its [[German National Action Plan on Energy Efficiency|National Action Plan on Energy Efficiency]] (NAPE).<ref name="nape">
{{cite web
| title= National Action Plan on Energy Efficiency (NAPE): making more out of energy
| website= Federal Ministry for Economic Affairs and Energy (BMWi)
| url= http://www.bmwi.de/EN/Topics/Energy/Energy-Efficiency/nape,did=667778.html
| access-date= 2016-06-07
}}</ref><ref name="bmwi-2014">
{{cite book
| title= Making more out of energy: National Action Plan on Energy Efficiency
| date= December 2014
| publisher= Federal Ministry for Economic Affairs and Energy (BMWi)
| place= Berlin, Germany
| url= http://www.bmwi.de/English/Redaktion/Pdf/nape-national-action-plan-on-energy-efficiency,property=pdf,bereich=bmwi2012,sprache=en,rwb=true.pdf
| access-date= 2016-06-07
}}</ref>
The areas covered are the energy efficiency of buildings, energy conservation for companies, consumer energy efficiency, and transport energy efficiency. The policy contains both immediate and forward-looking measures. The central short-term measures of NAPE include the introduction of competitive tendering for energy efficiency, the raising of funding for building renovation, the introduction of tax incentives for efficiency measures in the building sector, and the setting up energy efficiency networks together with business and industry. German industry is expected to make a sizeable contribution.

On 12 August 2016, the German government released a [[green paper]] on energy efficiency for public consultation (in German).<ref name="bmwi-2016-press-release">
{{cite press release
|author= <!-- staff writer, no by-line -->
|title= Gabriel: Efficiency First — discuss the Green Paper on Energy Efficiency with us!
|date= 12 August 2016
|publisher= Federal Ministry for Economic Affairs and Energy (BMWi)
|location= Berlin, Germany
|url= http://www.bmwi.de/EN/Press/press-releases,did=777756.html
|access-date= 2016-09-06
|url-status= dead
|archiveurl= https://web.archive.org/web/20160922232413/http://www.bmwi.de/EN/Press/press-releases,did=777756.html
|archivedate= 22 September 2016
}}
</ref><ref name="bmwi-2016-green-paper">
{{cite book
| title= Grünbuch Energieeffizienz: Diskussionspapier des Bundesministeriums für Wirtschaft und Energie
| trans-title= Green paper on energy efficiency: discussion document by the Federal Ministry for Economic Affairs and Energy
| language= German
| publisher= Federal Ministry for Economic Affairs and Energy (BMWi)
| location= Berlin, Germany
| url= https://www.bmwi.de/BMWi/Redaktion/PDF/Publikationen/gruenbuch-energieeffizienz,property=pdf,bereich=bmwi2012,sprache=de,rwb=true.pdf
| access-date= 2016-09-06
}}
</ref> It outlines the potential challenges and actions needed to reduce energy consumption in Germany over the coming decades. At the document's launch, economics and energy minister [[Sigmar Gabriel]] said "we do not need to produce, store, transmit and pay for the energy that we save".<ref name="bmwi-2016-press-release"/> The green paper prioritizes the efficient use of energy as the "first" response and also outlines opportunities for [[power-to-X#Sector coupling concepts|sector coupling]], including using renewable power for heating and transport.<ref name="bmwi-2016-press-release"/> Other proposals include a flexible energy tax which rises as petrol prices fall, thereby incentivizing fuel conservation despite low oil prices.<ref name="amelang-2016">
{{cite news
| first= Sören |last= Amelang
| title= Lagging efficiency to get top priority in Germany's Energiewende
| date= 15 August 2016
| website= Clean Energy Wire (CLEW)
| location= Berlin, Germany
| url= https://www.cleanenergywire.org/news/lagging-efficiency-get-top-priority-germanys-energiewende
| access-date= 2016-09-06
}}</ref>

===Poland===
In May 2016 Poland adopted a new Act on Energy Efficiency, to enter into force on 1{{nbsp}}October 2016.<ref name="sekula-baranska-2016">
{{cite web
| last= Sekuła-Baranska |first= Sandra
| title= New Act on Energy Efficiency passed in Poland
| date= 24 May 2016
| website= Noerr
| location= Munich, Germany
| url= https://www.noerr.com/en/press-publications/News/new-act-on-energy-efficiency-passed-in-poland.aspx
| access-date= 2016-09-20
}}
</ref>

===United States===
{{Main|Energy conservation in the United States}}

A 2011 [[Energy Modeling Forum]] study covering the United States examines how energy efficiency opportunities will shape future fuel and electricity demand over the next several decades. The US economy is already set to lower its energy and carbon intensity, but explicit policies will be necessary to meet climate goals. These policies include: a carbon tax, mandated standards for more efficient appliances, buildings and vehicles, and subsidies or reductions in the upfront costs of new more energy-efficient equipment.<ref>{{cite book
| first= Hillard |last= Huntington
| title= EMF 25: Energy efficiency and climate change mitigation — Executive summary report (volume 1)
| year= 2011
| publisher= [[Energy Modeling Forum]]
| place= Stanford, CA, USA
| url= https://web.stanford.edu/group/emf-research/docs/emf25/summary25.pdf
| access-date= 2016-05-10
}}</ref>

==Industry==
Industries use a large amount of energy to power a diverse range of manufacturing and resource extraction processes. Many industrial processes require large amounts of heat and mechanical power, most of which is delivered as [[natural gas]], [[petroleum|petroleum fuels]], and [[electricity]]. In addition some industries generate fuel from waste products that can be used to provide additional energy.

Because industrial processes are so diverse it is impossible to describe the multitude of possible opportunities for energy efficiency in industry. Many depend on the specific technologies and processes in use at each industrial facility. There are, however, a number of processes and energy services that are widely used in many industries.

Various industries generate [[steam]] and electricity for subsequent use within their facilities. When electricity is generated, the heat that is produced as a by-product can be captured and used for process steam, heating or other industrial purposes. Conventional electricity generation is about 30% efficient, whereas combined heat and power (also called [[co-generation]]) converts up to 90 percent of the fuel into usable energy.<ref name=indust>{{cite web|author=Environmental and Energy Study Institute |url=http://ladoma.org/wp-content/uploads/2015/01/Energy-Efficiency-Fact-Sheet.pdf |title=Industrial Energy Efficiency: Using new technologies to reduce energy use in industry and manufacturing |accessdate=2015-01-11}}</ref>

Advanced boilers and furnaces can operate at higher temperatures while burning less fuel. These technologies are more efficient and produce fewer pollutants.<ref name=indust/>

Over 45 percent of the fuel used by US manufacturers is burnt to make steam. The typical industrial facility can reduce this energy usage 20 percent (according to the [[US Department of Energy]]) by insulating steam and condensate return lines, stopping steam leakage, and maintaining steam traps.<ref name=indust/>

[[Electric motor]]s usually run at a constant speed, but a [[variable speed drives|variable speed drive]] allows the motor's energy output to match the required load. This achieves energy savings ranging from 3 to 60 percent, depending on how the motor is used. Motor coils made of [[superconducting]] materials can also reduce energy losses.<ref name=indust/> Motors may also benefit from [[voltage optimisation]]. {{Citation needed|date=December 2013}}

Industry uses a large number of [[pumps]] and [[compressors]] of all shapes and sizes and in a wide variety of applications. The efficiency of pumps and compressors depends on many factors but often improvements can be made by implementing better [[process control]] and better maintenance practices. Compressors are commonly used to provide [[compressed air]] which is used for sand blasting, painting, and other power tools. According to the US Department of Energy, optimizing compressed air systems by installing variable speed drives, along with [[maintenance (technical)|preventive maintenance]] to detect and fix air leaks, can improve energy efficiency 20 to 50 percent.<ref name=indust/>

==Transportation==
{{Main|Energy efficiency in transportation}}

===Automobiles===
{{Main|Fuel economy in automobiles}}

[[File:NYPD Traffic Enforcement RMP In White.jpeg|thumb|left|[[Toyota Prius]] used by [[NYPD#Traffic Enforcement|NYPD Traffic Enforcement]]]]

The estimated energy efficiency for an automobile is 280 Passenger-Mile/10<sup>6</sup> Btu.<ref>Richard C. Dorf, ''The Energy Factbook'', McGraw-Hill, 1981</ref> There are several ways to enhance a vehicle's energy efficiency. Using improved [[aerodynamics]] to minimize drag can increase vehicle [[fuel efficiency]]. Reducing vehicle weight can also improve fuel economy, which is why [[composite materials]] are widely used in car bodies.

More advanced tires, with decreased tire to road friction and rolling resistance, can save gasoline. Fuel economy can be improved by up to 3.3% by keeping tires inflated to the correct pressure.<ref>{{cite web|url=http://www.fueleconomy.gov/feg/maintain.shtml |title=Tips to improve your Gas Mileage |publisher=Fueleconomy.gov |accessdate=2010-07-16}}</ref> Replacing a clogged air filter can improve a cars fuel consumption by as much as 10 percent on older vehicles.<ref>{{cite web|url=http://www.eesi.org/files/auto_efficiency_0506.pdf|format=PDF|title=Automotive Efficiency : Using technology to reduce energy use in passenger vehicles and light trucks |website=Eesi.org|accessdate=26 March 2019}}</ref> On newer vehicles (1980s and up) with fuel-injected, computer-controlled engines, a clogged air filter has no effect on mpg but replacing it may improve acceleration by 6-11 percent.<ref>{{cite web|url=http://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_26_2009.pdf|format=PDF|title=Effect of Intake Air Filter Condition on Vehicle Fuel Economy|website=Fueleconomy.gov|accessdate=26 March 2019}}</ref> Aerodynamics also aid in efficiency of a vehicle. The design of a car impacts the amount of gas needed to move it through air. Aerodynamics involves the air around the car, which can affect the efficiency of the energy expended.<ref>{{Cite news|url=https://www.carsdirect.com/car-buying/what-makes-a-car-fuel-efficient|title=What Makes a Fuel Efficient Car? The 8 Most Fuel Efficient Cars|work=CarsDirect|access-date=2018-10-03|language=en}}</ref>

[[Turbocharger]]s can increase fuel efficiency by allowing a smaller displacement engine. The 'Engine of the year 2011' is a Fiat 500 engine equipped with an MHI turbocharger. "Compared with a 1.2-liter 8v engine, the new 85 HP turbo has 23% more power and a 30% better performance index. The performance of the two-cylinder is not only equivalent to a 1.4-liter 16v engine, but fuel consumption is 30% lower."<ref>{{cite web|title=Fiat 875cc TwinAir named International Engine of the Year 2011|url=http://www.greencarcongress.com/2011/05/fiat-20110520.html|website=Green Car Congress}}</ref>

Energy-efficient vehicles may reach twice the fuel efficiency of the average automobile. Cutting-edge designs, such as the diesel [[Mercedes-Benz Bionic]] concept vehicle have achieved a fuel efficiency as high as {{convert|84|mpgus}}, four times the current conventional automotive average.<ref>[https://web.archive.org/web/20150706103029/http://www.eesi.org/files/auto_efficiency_0506.pdf]</ref>

The mainstream trend in automotive efficiency is the rise of [[electric vehicle]]s (all@electric or hybrid electric). Electric engines have more than double the efficiency of internal combustion engines.<ref>[https://www.quora.com/How-energy-efficient-are-electric-motors-compared-to-combustion-engines Efficiency of electric motors vs internal combustion engines]</ref>{{better source needed|date=November 2019}} Hybrids, like the [[Toyota Prius]], use [[regenerative braking]] to recapture energy that would dissipate in normal cars; the effect is especially pronounced in city driving.<ref>{{cite web |author=Nom * |url=https://www.lenergieenquestions.fr/prius-toyota-modele-reference-voitures-hybrides/ |title=La Prius de Toyota, une référence des voitures hybrides &#124; L'énergie en questions |publisher=Lenergieenquestions.fr |date=2013-06-28 |accessdate=2013-08-21 |url-status=dead |archiveurl=https://web.archive.org/web/20131017080726/https://www.lenergieenquestions.fr/prius-toyota-modele-reference-voitures-hybrides/ |archivedate=2013-10-17 }}</ref> [[Plug-in hybrid]]s also have increased battery capacity, which makes it possible to drive for limited distances without burning any gasoline; in this case, energy efficiency is dictated by whatever process (such as coal-burning, hydroelectric, or renewable source) created the power. Plug-ins can typically drive for around {{convert|40|mi}} purely on electricity without recharging; if the battery runs low, a gas engine kicks in allowing for extended range. Finally, all-electric cars are also growing in popularity; the [[Tesla Model S]] sedan is the only high-performance all-electric car currently on the market.

===Street lighting===
Cities around the globe light up millions of streets with 300 million lights.<ref>{{cite web|url=https://www.researchandmarkets.com/reports/4456402/global-led-and-smart-street-lighting-market|title=Global LED and Smart Street Lighting: Market Forecast (2017 - 2027)|first=Research and Markets|last=ltd|website=Researchandmarkets.com|accessdate=26 March 2019}}</ref> Some cities are seeking to reduce [[street light]] power consumption by dimming lights during off-peak hours or switching to LED lamps.<ref>{{cite web|url=https://www.edmonton.ca/transportation/on_your_streets/street-lighting.aspx|title=Street Lighting|first=City of|last=Edmonton|date=26 March 2019|website=Edmonton.ca|accessdate=26 March 2019}}</ref> It is not clear whether the high luminous efficiency of LEDs will lead to real reductions in energy, as cities may end up installing extra lamps or lighting areas more brightly than in the past.<ref>{{cite journal|last1=Kyba|first1=C. C. M.|last2=Hänel|first2=A.|last3=Hölker|first3=F.|title=Redefining efficiency for outdoor lighting|journal=Energy & Environmental Science|date=2014|volume=7|issue=6|pages=1806|doi=10.1039/C4EE00566J}}</ref>

===Aircraft===
{{Main|Fuel economy in aircraft|Environmental impact of aviation}}
There are several ways to reduce energy usage in air transportation, from modifications to the planes themselves, to how air traffic is managed. As in cars, turbochargers are an effective way to reduce energy consumption; however, instead of allowing for the use of a smaller-displacement engine, turbochargers in jet turbines operate by compressing the thinner air at higher altitudes. This allows the engine to operate as if it were at sea-level pressures while taking advantage of the reduced drag on the aircraft at higher altitudes.

Air traffic management systems are another way to increase the efficiency of not just the aircraft but the airline industry as a whole. New technology allows for superior automation of takeoff, landing, and collision avoidance, as well as within airports, from simple things like HVAC and lighting to more complex tasks such as security and scanning.

==Alternative fuels==
{{Main|Alternative fuels}}
[[File:Piracicaba 10 2008 151 Gast station selling four fuels.jpg|thumb|Typical [[Brazil]]ian filling station with four [[alternative fuel]]s for sale: [[biodiesel]] (B3), [[gasohol]] (E25), neat [[ethanol fuel|ethanol]] ([[neat alcohol fuel|E100]]), and [[compressed natural gas]] (CNG). [[Piracicaba]], [[Brazil]].]]
Alternative fuels, known as non-conventional or advanced [[fuel]]s, are any materials or [[Chemical substance|substance]]s that can be used as [[fuel]]s, other than conventional fuels. Some well known alternative [[fuel]]s include [[biodiesel]], [[bioalcohol]] ([[methanol]], [[ethanol]], [[n-Butanol|butanol]]), chemically stored [[electricity]] (batteries and [[fuel cell]]s), [[hydrogen]], non-fossil [[methane]], non-fossil [[natural gas]], [[vegetable oil used as fuel|vegetable oil]], and other [[biomass]] sources. The production efficiency of these fuels greatly differs.

==Energy conservation==
{{Main|Energy conservation}}
[[File:Illust passive solar d1.gif|thumb|250px|right|Elements of [[Passive solar building design|passive solar energy design]], shown in a direct gain application]]

[[Energy conservation]] is broader than energy efficiency in including active efforts to decrease energy consumption, for example through [[behavior change (public health)|behaviour change]], in addition to using energy more efficiently. Examples of conservation without efficiency improvements are heating a room less in winter, using the car less, air-drying your clothes instead of using the dryer, or enabling energy saving modes on a computer. As with other definitions, the boundary between efficient energy use and energy conservation can be fuzzy, but both are important in environmental and economic terms.<ref>Dietz, T. et al. (2009).[http://www.pnas.org/content/106/44/18452.full Household actions can provide a behavioral wedge to rapidly reduce US carbon emissions]. PNAS. 106(44).</ref> This is especially the case when actions are directed at the saving of [[fossil fuels]].<ref>Diesendorf, Mark (2007). ''Greenhouse Solutions with Sustainable Energy'', UNSW Press, p. 87.</ref> Energy conservation is a challenge requiring policy programmes, technological development and behavior change to go hand in hand. Many energy [[intermediary]] organisations, for example governmental or non-governmental organisations on local, regional, or national level, are working on often publicly funded programmes or projects to meet this challenge.<ref>Breukers, Heiskanen, et al. (2009). Interaction schemes for successful demand-side management. Deliverable 5 of the [http://www.energychange.info/index.php CHANGING BEHAVIOUR] {{Webarchive|url=https://web.archive.org/web/20101130100555/http://www.energychange.info/index.php |date=2010-11-30 }} project. Funded by the EC (#213217).</ref> Psychologists have also engaged with the issue of energy conservation and have provided guidelines for realizing behavior change to reduce energy consumption while taking technological and policy considerations into account.<ref>Kok, G., Lo, S.H., Peters, G.J. & R.A.C. Ruiter (2011), Changing Energy-Related Behavior: An Intervention Mapping Approach, Energy Policy, 39:9, 5280-5286, doi:10.1016/j.enpol.2011.05.036</ref>

The National Renewable Energy Laboratory maintains a comprehensive list of apps useful for energy efficiency.<ref>{{cite web|url=http://en.openei.org/apps/ |title=National Renewable Energy Laboratory. (2012) |publisher=En.openei.org |accessdate=2013-08-21}}</ref>

Commercial property managers that plan and manage energy efficiency projects generally use a software platform to perform energy audits and to collaborate with contractors to understand their full range of options. The [http://apps1.eere.energy.gov/buildings/tools_directory/software.cfm/ID=622/pagename=alpha_list_sub Department of Energy (DOE) Software Directory] describes EnergyActio software, a cloud based platform designed for this purpose.

==Sustainable energy==
{{Main|Sustainable energy}}

Energy efficiency and [[renewable energy]] are said to be the “twin pillars” of a sustainable [[energy policy]]. Both strategies must be developed concurrently in order to stabilize and reduce [[carbon dioxide emissions]]. Efficient energy use is essential to slowing the energy demand growth so that rising [[clean energy]] supplies can make deep cuts in fossil fuel use. If energy use grows too rapidly, renewable energy development will chase a receding target. Likewise, unless clean energy supplies come online rapidly, slowing demand growth will only begin to reduce total carbon emissions; a reduction in the carbon content of energy sources is also needed. A sustainable energy economy thus requires major commitments to both efficiency and renewables.<ref>{{cite web |url=http://www.paenergyfuture.psu.edu/pubs/aceee_reports/aceee2007sustainable.pdf |title=Archived copy |accessdate=2014-12-17 |url-status=dead |archiveurl=https://web.archive.org/web/20150111000420/http://www.paenergyfuture.psu.edu/pubs/aceee_reports/aceee2007sustainable.pdf |archivedate=2015-01-11 }}([[American Council for an Energy-Efficient Economy]])</ref>

==Rebound effect==
{{Further|Rebound effect (conservation)|Jevons' paradox}}
If the demand for energy services remains constant, improving energy efficiency will reduce energy consumption and carbon emissions. However, many efficiency improvements do not reduce energy consumption by the amount predicted by simple engineering models. This is because they make energy services cheaper, and so consumption of those services increases. For example, since fuel efficient vehicles make travel cheaper, consumers may choose to drive farther, thereby offsetting some of the potential energy savings. Similarly, an extensive historical analysis of technological efficiency improvements has conclusively shown that energy efficiency improvements were almost always outpaced by economic growth, resulting in a net increase in resource use and associated pollution.<ref>Huesemann, Michael H., and Joyce A. Huesemann (2011). [http://www.newtechnologyandsociety.org ''Technofix: Why Technology Won't Save Us or the Environment''], Chapter 5, "In Search of Solutions II: Efficiency Improvements", New Society Publishers, Gabriola Island, Canada.</ref> These are examples of the direct [[rebound effect (conservation)|rebound effect]].<ref name=direct>[http://www.ukerc.ac.uk/Downloads/PDF/07/0710ReboundEffect/0710ReboundEffectReport.pdf The Rebound Effect: an assessment of the evidence for economy-wide energy savings from improved energy efficiency] {{webarchive|url=https://web.archive.org/web/20080910051917/http://www.ukerc.ac.uk/Downloads/PDF/07/0710ReboundEffect/0710ReboundEffectReport.pdf |date=2008-09-10}} pp. v-vi.</ref>

Estimates of the size of the rebound effect range from roughly 5% to 40%.<ref name=Greening>{{Cite journal |doi=10.1016/S0301-4215(00)00021-5 |first=Lorna A. |last=Greening |title=Energy efficiency and consumption—the rebound effect—a survey |author2=David L. Greene |author3=Carmen Difiglio |journal=Energy Policy |volume=28 |year=2000 |pages=389–401 |issue=6–7}}</ref><ref>{{cite web|url= http://repositories.cdlib.org/ucei/policy/EPE-014 |title= The Effect of Improved Fuel Economy on Vehicle Miles Traveled: Estimating the Rebound Effect Using US State Data, 1966-2001 |author= Kenneth A. Small and Kurt Van Dender |date= September 21, 2005 |publisher= University of California Energy Institute: Policy & Economics |accessdate=2007-11-23}}</ref><ref>{{cite web |url=http://www.policyarchive.org/handle/10207/bitstreams/3492.pdf |title= Energy Efficiency and the Rebound Effect: Does Increasing Efficiency Decrease Demand? |accessdate=2011-10-01}}</ref> The rebound effect is likely to be less than 30% at the household level and may be closer to 10% for transport.<ref name=direct/> A rebound effect of 30% implies that improvements in energy efficiency should achieve 70% of the reduction in energy consumption projected using engineering models. The rebound effect may be particularly large for lighting, because in contrast to tasks like transport there is effectively no upper limit on how much light could be considered useful.<ref>{{cite journal|last=Kyba|first=C. C. M.|author2=Hänel, A. |author3=Hölker, F. |title=Redefining efficiency for outdoor lighting|journal=Energy & Environmental Science|doi=10.1039/C4EE00566J}}</ref> In fact, it appears that lighting has accounted for about 0.7% of GDP across many societies and hundreds of years, implying a rebound effect of 100%.<ref>{{cite journal|last=Tsao|first=J Y|author2=Saunders, H D |author3=Creighton, J R |author4=Coltrin, M E |author5= Simmons, J A |title=Solid-state lighting: an energy-economics perspective|journal=Journal of Physics D: Applied Physics|date=8 September 2010|volume=43|issue=35|pages=354001|doi=10.1088/0022-3727/43/35/354001|bibcode=2010JPhD...43I4001T}}</ref>

==Organisations and programs==
'''International'''
*[[80 Plus]]
*[[2000-watt society]]
*[[IEA Solar Heating & Cooling Implementing Agreement Task 13]]
*[[International Institute for Energy Conservation]]
*[[International Energy Agency]] (e.g. [[One Watt initiative]])
*[[International Electrotechnical Commission]]
*[[International Partnership for Energy Efficiency Cooperation]]
*[[World Sustainable Energy Days]]

'''China'''
*[[National Development and Reform Commission]]
*[[National Energy Conservation Center]]
*[[Energy Research Institute, NDRC]]

'''Australia'''
*[[Department of Climate Change and Energy Efficiency]]
*[[Department of the Environment, Water, Heritage and the Arts]]
*[[Sustainable House Day]]

'''European Union'''
*[[Building energy rating]]
*[[Eco-Design of Energy-Using Products Directive]]
*[[Energy efficiency in Europe (study)]]
*[[Orgalime]], the European engineering industries association

'''Finland'''
*[[Motiva]]

'''Iceland'''
*[[Marorka]]

'''India'''
*[[88888 Lights Out]]
*[[Bureau of Energy Efficiency]]
*[[Energy Efficiency Services Limited]]

'''Indonesia'''
*[http://maskeei.org/ Indonesia Energy Conservation and Efficiency Society (IECES)]

'''Japan'''
*[[Cool Biz campaign]]

'''Lebanon'''
*[[The Lebanese Center for Energy Conservation]]

'''United Kingdom'''
*[[The Carbon Trust]]
*[[Energy Saving Trust]]
*[[National Energy Action]]
*[[National Energy Foundation]]
*[[Creative Energy Homes]]
*[http://www.theema.org.uk/ Energy Managers Association]

'''United States'''
*[[Alliance to Save Energy]]
*[[American Council for an Energy-Efficient Economy|American Council for an Energy-Efficient Economy (ACEEE)]]
*[[Building Codes Assistance Project]]
*[[Building Energy Codes Program]]
*[[Consortium for Energy Efficiency]]
*[[Energy Star]], from [[United States Environmental Protection Agency]]
*[[Industrial Assessment Center]]
*[[National Electrical Manufacturers Association]]
*[[Rocky Mountain Institute]]
*[[Indian energy strategies]]

==See also==
{{Portal|Renewable energy|Energy|Ecology}}

{{Div col|colwidth=30em}}
*[[Cogeneration]]
*[[Data center infrastructure efficiency]]
*[[Distributed generation]]
*[[Electrical energy efficiency on United States farms]]
*[[Electric vehicle#Efficiency]]
*[[Energy audit]]
*[[Energy conservation measure]]s
*[[Energy conversion efficiency]]
*[[Energy efficiency implementation]]
*[[Energy recovery]]
*[[Energy resilience]]
*[[Energy storage]]
*[[Energy storage as a service]] (ESaaS)
*[[EU Energy Efficiency Directive 2012/27/EU]]
*[[Khazzoom–Brookes postulate]]
*[[Performance per watt]]
*[[Lee Schipper]]
*[[List of energy storage projects]]
*[[List of least carbon efficient power stations]]
*[[Negawatt power]]
*[[Passenger miles per gallon]]
*[[Peak oil]]
*[[Renewable energy]]
*[[Renewable heat]]
*[[Standby power]]
*US Department of Energy [[Solar Decathlon]]
*[[The Green Deal]]
*[[World Energy Engineering Congress]]
*[[Energy Reduction Assets]]
*[[John A. "Skip" Laitner]]
*[[Passive house]]
*[[Light pollution]]
{{div col end}}

==References==
{{Reflist|30em}}

{{Authority control}}

{{DEFAULTSORT:Efficient Energy Use}}
[[Category:Energy conservation| ]]
[[Category:Energy efficiency]]
[[Category:Energy policy]]
[[Category:Industrial ecology]]
[[Category:Sustainable energy]]

[[es:Mitigación del cambio climático#Eficiencia energética y conservación]]