Editing Refrigerator (section)

== Energy efficiency ==
[[File:Energy label 2010.svg|thumb|A European energy label for a refrigerator]]

In a house without air-conditioning (space heating and/or cooling) refrigerators consume more energy than any other home device.<ref>{{cite web|title=Which UK – Saving Energy|url=http://www.which.co.uk/energy/saving-money/guides/energy-labels-explained/fridge-and-freezer-energy-labels|work=Which UK|access-date=10 November 2014|url-status=live|archive-url=https://web.archive.org/web/20141110161250/http://www.which.co.uk/energy/saving-money/guides/energy-labels-explained/fridge-and-freezer-energy-labels|archive-date=10 November 2014}}</ref> In the early 1990s a competition was held among the major US manufacturers to encourage energy efficiency.<ref>{{cite journal |author1=Feist, J. W. |author2=Farhang, R. |author3=Erickson, J. |author4=Stergakos, E. |title=Super Efficient Refrigerators: The Golden Carrot from Concept to Reality |journal=Proceedings of the ACEEE |year=1994 |volume=3 |pages=3.67–3.76 |url=http://cgec.ucdavis.edu/ACEEE/1994-96/1994/VOL03/067.PDF |url-status=dead |archive-url=https://web.archive.org/web/20130925105645/http://cgec.ucdavis.edu/ACEEE/1994-96/1994/VOL03/067.PDF |archive-date=25 September 2013}}</ref> Current US models that are [[Energy Star]] qualified use 50% less energy than the average 1974 model used.<ref>{{Cite news|title=Refrigerators & Freezers |work=[[Energy Star]] |url=http://www.energystar.gov/index.cfm?c=refrig.pr_refrigerators |url-status=dead |archive-url=https://web.archive.org/web/20060207074043/http://www.energystar.gov/index.cfm?c=refrig.pr_refrigerators |archive-date=7 February 2006 }}</ref> The most energy-efficient unit made in the US consumes about half a kilowatt-hour per day (equivalent to 20&nbsp;W continuously).<ref>Itakura, Kosuke. [https://web.archive.org/web/20070118051403/http://www.humboldt.edu/~ccat/energyconservation/sunfrost/kosukiSP2002/index.html Sun Frost – The World's Most Efficient Refrigerators]. Humboldt.edu</ref> But even ordinary units are reasonably efficient; some smaller units use less than 0.2&nbsp;kWh per day (equivalent to 8&nbsp;W continuously).
Larger units, especially those with large freezers and icemakers, may use as much as 4&nbsp;kW·h per day (equivalent to 170&nbsp;W continuously).
The European Union uses a letter-based mandatory [[European Union energy label|energy efficiency rating label]], with A being the most efficient, instead of the Energy Star. 

For US refrigerators, the Consortium on Energy Efficiency (CEE) further differentiates between Energy Star qualified refrigerators. Tier 1 refrigerators are those that are 20% to 24.9% more efficient than the Federal minimum standards set by the [[National Appliance Energy Conservation Act]] (NAECA). Tier 2 are those that are 25% to 29.9% more efficient. Tier 3 is the highest qualification, for those refrigerators that are at least 30% more efficient than Federal standards.<ref>{{cite web | title=High-efficiency specifications for REFRIGERATORS | url=http://www.cee1.org/resid/seha/refrig/refrig-spec.pdf | work=Consortium for Energy Efficiency | date=January 2007 | url-status=live | archive-url=https://web.archive.org/web/20130115173201/http://www.cee1.org/resid/seha/refrig/refrig-spec.pdf | archive-date=15 January 2013 | df=dmy-all }}</ref> About 82% of the Energy Star qualified refrigerators are Tier 1, with 13% qualifying as Tier 2, and just 5% at Tier 3.{{citation needed|date=June 2020}}

Besides the standard style of compressor refrigeration used in ordinary household refrigerators and freezers, there are technologies such as [[Absorption refrigeration|absorption]] and [[magnetic refrigeration]]. Although these designs generally use a much more energy than compressor refrigeration, other qualities such as silent operation or the ability to use gas can favor their use in small enclosures, a mobile environment or in environments where failure of refrigeration must not be possible.{{Citation needed|date=August 2021}}

Many refrigerators made in the 1930s and 1940s were far more efficient than most that were made later. This is partly due to features added later, such as auto-defrost, that reduced efficiency. Additionally, after World War 2, refrigerator style became more important than efficiency. This was especially true in the US in the 1970s, when side-by-side models (known as American fridge-freezers outside of the US) with ice dispensers and water chillers became popular. The amount of insulation used was also often decreased to reduce refrigerator case size and manufacturing costs.{{Citation needed|date=August 2021}}

===Improvement===
[[File:ExpensiveRefrigerators.JPG|thumb|Display of modern American-style / side-by-side refrigerators, available for purchase in a store]]

Over time standards of refrigerator energy efficiency have been introduced and tightened, which has driven steady improvement; 21st-century refrigerators are typically three times more energy-efficient than in the 1930s.<ref>{{Cite news | title=Successes of Energy Efficiency: The United States and California National Trust | url=http://www.energy.ca.gov/2007publications/CEC-999-2007-023/CEC-999-2007-023.PDF | url-status=live | archive-url=https://web.archive.org/web/20120225075006/http://www.energy.ca.gov/2007publications/CEC-999-2007-023/CEC-999-2007-023.PDF | archive-date=25 February 2012 | df=dmy-all }}</ref><ref>{{Cite news  |title=Out With the Old, In With the New  |url=http://www.nrdc.org/air/energy/appliance/app1.pdf  |author1=Calwell, Chris  |author2=Reeder, Travis  |name-list-style=amp  |year=2001  |work=Natural Resources Defense Council  |url-status=live  |archive-url=https://web.archive.org/web/20110608090449/http://www.nrdc.org/air/energy/appliance/app1.pdf  |archive-date=8 June 2011  }}</ref>

The efficiency of older refrigerators can be improved by regular defrosting (if the unit is manual defrost) and cleaning, replacing deteriorated door seals with new ones, not setting the thermostat colder than actually required (a refrigerator does not usually need to be colder than {{convert|4|°C|°F}}), and replacing insulation, where applicable. Cleaning condenser coils to remove dust impeding heat flow, and ensuring that there is space for air flow around the condenser can improve efficiency.

==== Auto defrosting ====
{{main|Auto-defrost}}
Frost-free refrigerators and freezers use electric fans to cool the appropriate compartment.<ref>{{Cite book|url=https://books.google.com/books?id=7bvxCAAAQBAJ&pg=PA21|title=Low Temperature and Cryogenic Refrigeration|last1=Kakaç|first1=Sadik|last2=Avelino|first2=M. R.|last3=Smirnov|first3=H. F.|date=6 December 2012|publisher=Springer Science & Business Media|isbn=9789401000994|language=en|access-date=13 December 2017|archive-date=25 April 2023|archive-url=https://web.archive.org/web/20230425113424/https://books.google.com/books?id=7bvxCAAAQBAJ&pg=PA21|url-status=live}}</ref> This could be called a "fan forced" refrigerator, whereas manual defrost units rely on colder air lying at the bottom, versus the warm air at the top to achieve adequate cooling. The air is drawn in through an inlet duct and passed through the evaporator where it is cooled, the air is then circulated throughout the cabinet via a series of ducts and vents. Because the air passing the evaporator is supposedly warm and moist, frost begins to form on the evaporator (especially on a freezer's evaporator). In cheaper and/or older models, a defrost cycle is controlled via a mechanical timer. This timer is set to shut off the compressor and fan and energize a heating element located near or around the evaporator for about 15 to 30 minutes at every 6 to 12 hours. This melts any frost or ice build-up and allows the refrigerator to work normally once more. It is believed that frost free units have a lower tolerance for frost, due to their air-conditioner-like evaporator coils. Therefore, if a door is left open accidentally (especially the freezer), the defrost system may not remove all frost, in this case, the freezer (or refrigerator) must be defrosted.<ref name="Badri">{{Cite journal |last1=Badri |first1=Deyae |last2=Toublanc |first2=Cyril |last3=Rouaud |first3=Olivier |last4=Havet |first4=Michel |date=2021-11-01 |title=Review on frosting, defrosting and frost management techniques in industrial food freezers |url=https://www.sciencedirect.com/science/article/pii/S1364032121008236 |journal=Renewable and Sustainable Energy Reviews |volume=151 |pages=111545 |doi=10.1016/j.rser.2021.111545 |bibcode=2021RSERv.15111545B |issn=1364-0321}}</ref>

If the defrosting system melts all the ice before the timed defrosting period ends, then a small device (called a defrost limiter) acts like a thermostat and shuts off the heating element to prevent too large a temperature fluctuation, it also prevents hot blasts of air when the system starts again, should it finish defrosting early. On some early frost-free models, the defrost limiter also sends a signal to the defrost timer to start the compressor and fan as soon as it shuts off the heating element before the timed defrost cycle ends. When the defrost cycle is completed, the compressor and fan are allowed to cycle back on.<ref name="Badri" />

Frost-free refrigerators, including some early frost-free refrigerators/freezers that used a cold plate in their refrigerator section instead of airflow from the freezer section, generally don't shut off their refrigerator fans during defrosting. This allows consumers to leave food in the main refrigerator compartment uncovered, and also helps keep vegetables moist. This method also helps reduce energy consumption, because the refrigerator is above freeze point and can pass the warmer-than-freezing air through the evaporator or cold plate to aid the defrosting cycle.{{Citation needed|date=August 2021}}

==== Inverter ====
[[File:Холодильник в сельском магазине.jpg|thumb|Refrigerator in a rural store]]
With the advent of digital [[inverter compressor]]s, the energy consumption is even further reduced than a single-speed induction motor compressor, and thus contributes far less in the way of greenhouse gases.<ref>{{Cite web|url=https://news.samsung.com/global/how-the-digital-inverter-compressor-has-transformed-the-modern-refrigerator|title=How the Digital Inverter Compressor Has Transformed the Modern Refrigerator|website=news.samsung.com|access-date=25 January 2020|archive-date=15 February 2020|archive-url=https://web.archive.org/web/20200215211111/https://news.samsung.com/global/how-the-digital-inverter-compressor-has-transformed-the-modern-refrigerator|url-status=live}}</ref>

The energy consumption of a refrigerator is also dependent on the type of refrigeration being done. For instance, Inverter Refrigerators consume comparatively less energy than a typical non-inverter refrigerator.  In an inverter refrigerator, the compressor is used conditionally on requirement basis. For instance, an inverter refrigerator might use less energy during the winters than it does during the summers. This is because the compressor works for a shorter time than it does during the summers.

Further, newer models of inverter compressor refrigerators take into account various external and internal conditions to adjust the compressor speed and thus optimize cooling and energy consumption. Most of them use at least 4 sensors which help detect variance in external temperature, internal temperature owing to opening of the refrigerator door or keeping new food inside; humidity and usage patterns. Depending on the sensor inputs, the compressor adjusts its speed. For example, if door is opened or new food is kept, the sensor detects an increase in temperature inside the cabin and signals the compressor to increase its speed till a pre-determined temperature is attained. After which, the compressor runs at a minimum speed to just maintain the internal temperature. The compressor typically runs between 1200 and 4500&nbsp;rpm.
Inverter compressors not only optimizes cooling but is also superior in terms of durability and energy efficiency.<ref>Chang, Wen Ruey; Liu, Der Yeong; Chen, San Guei; and Wu, Nan Yi, "The Components and Control Methods for Implementation of Inverter-Controlled Refrigerators/Freezers" (2004). International Refrigeration and Air Conditioning Conference. Paper 696. http://docs.lib.purdue.edu/iracc/696</ref>
A device consumes maximum energy and undergoes maximum wear and tear when it switches itself on. As an inverter compressor never switches itself off and instead runs on varying speed, it minimizes wear and tear and energy usage.
[[LG Corporation|LG]]  played a significant role in improving inverter compressors as we know it by reducing the friction points in the compressor and thus introducing [[Linear compressor|Linear Inverter Compressors.]] Conventionally, all domestic refrigerators use a reciprocating drive which is connected to the piston. But in a linear inverter compressor, the piston which is a permanent magnet is suspended between two electromagnets. The AC changes the magnetic poles of the electromagnet, which results in the push and pull that compresses the refrigerant.  LG claims that this helps reduce energy consumption by 32% and noise by 25% compared to their conventional compressors.

=== Form factor ===
The physical design of refrigerators also plays a large part in its energy efficiency. The most efficient is the chest-style freezer, as its top-opening design minimizes convection when opening the doors, reducing the amount of warm moist air entering the freezer. On the other hand, in-door ice dispensers cause more heat leakage, contributing to an increase in energy consumption.<ref>{{cite web |author=[[Technology Connections]] |title=Chest Freezers; What they tell us about designing for X |url=https://www.youtube.com/watch?v=CGAhWgkKlHI |website=YouTube |date=April 7, 2020 |access-date=13 May 2020 |archive-date=12 May 2020 |archive-url=https://web.archive.org/web/20200512202858/https://www.youtube.com/watch?v=CGAhWgkKlHI |url-status=live }}</ref>