Editing Heat pump (section)

==Performance==
{{Main|Coefficient of performance}}
The performance of a heat pump is determined by the ability of the pump to extract heat from a low temperature environment (the ''source'') and deliver it to a higher temperature environment (the ''sink'').<ref name="nrc">{{Cite web|date=8 September 2022|access-date=3 April 2023|title=Heating and cooling with a heat pump: Efficiency terminology|url=https://natural-resources.canada.ca/energy-efficiency/energy-star-canada/about/energy-star-announcements/publications/heating-and-cooling-heat-pump/6817#b6|publisher=Natural Resources Canada|archive-date=3 April 2023|archive-url=https://web.archive.org/web/20230403181606/https://natural-resources.canada.ca/energy-efficiency/energy-star-canada/about/energy-star-announcements/publications/heating-and-cooling-heat-pump/6817#b6|url-status=live}}</ref> Performance varies, depending on installation details, temperature differences, site elevation, location on site, pipe runs, flow rates, and maintenance.  

In general, heat pumps work most efficiently (that is, the heat output produced for a given energy input) when the difference between the heat source and the heat sink is small. When using a heat pump for space or water heating, therefore, the heat pump will be most efficient in mild conditions, and decline in efficiency on very cold days. Performance metrics supplied to consumers attempt to take this variation into account.

Common performance metrics are the SEER (in cooling mode) and seasonal coefficient of performance (SCOP) (commonly used just for heating), although SCOP can be used for both modes of operation.<ref name=nrc/> Larger values of either metric indicate better performance.<ref name=nrc/> When comparing the performance of heat pumps, the term ''performance'' is preferred to ''efficiency'', with [[coefficient of performance]] (COP) being used to describe the ratio of useful heat movement per work input.<ref name=nrc/> An [[electrical resistance heater]] has a COP of 1.0, which is considerably lower than a well-designed heat pump which will typically have a COP of 3 to 5 with an external temperature of 10&nbsp;°C and an internal temperature of 20&nbsp;°C. Because the ground is a constant temperature source, a ground-source heat pump is not subjected to large temperature fluctuations, and therefore is the most energy-efficient type of heat pump.<ref name=nrc/>

The "seasonal coefficient of performance" (SCOP) is a measure of the aggregate energy efficiency measure over a period of one year which is dependent on regional climate.<ref name=nrc/> One framework for this calculation is given by the Commission Regulation (EU) No. 813/2013.<ref>{{CELEX|id=32013R0813|text=Commission Regulation (EU) No 813/2013 of 2 August 2013 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for space heaters and combination heaters}}</ref>

A heat pump's operating performance in cooling mode is characterized in the US by either its [[energy efficiency ratio]] (EER) or [[seasonal energy efficiency ratio]] (SEER), both of which have units of BTU/(h·W) (note that 1 BTU/(h·W)&nbsp;= 0.293 W/W) and larger values indicate better performance.

{| class="wikitable" style="text-align:center; margin-right:auto"
|+ COP variation with output temperature
|-
! scope="col" | Pump type and source
! scope="col" | Typical use
! scope="col" | 35&nbsp;°C <br /> (e.g. heated [[screed]] floor)
! scope="col" | 45&nbsp;°C <br /> (e.g. heated screed floor)
! scope="col" | 55&nbsp;°C <br /> (e.g. heated timber floor)
! scope="col" | 65&nbsp;°C <br /> (e.g. radiator or [[Water heating|DHW]])
! scope="col" | 75&nbsp;°C <br /> (e.g. radiator and DHW)
! scope="col" | 85&nbsp;°C <br /> (e.g. radiator and DHW)
|-
|style="text-align:left"| High-efficiency air-source heat pump (ASHP), air at −20&nbsp;°C<ref name="CREN">The Canadian Renewable Energy Network [http://dsp-psd.pwgsc.gc.ca/Collection/M92-251-2002E.pdf 'Commercial Earth Energy Systems', Figure 29] {{Webarchive|url=https://web.archive.org/web/20110511210543/http://dsp-psd.pwgsc.gc.ca/Collection/M92-251-2002E.pdf |date=2011-05-11 }}. . Retrieved December 8, 2009.</ref>
|style="text-align:left"|
| 2.2
| 2.0
| ‐
| ‐
| ‐
| ‐
|-
|style="text-align:left"| Two-stage ASHP, air at −20&nbsp;°C<ref name="TIPC">Technical Institute of Physics and Chemistry, Chinese Academy of Sciences [http://repository.tamu.edu/bitstream/handle/1969.1/5474/ESL-IC-06-11-312.pdf?sequence=4 'State of the Art of Air-source Heat Pump for Cold Region', Figure 5] {{Webarchive|url=https://web.archive.org/web/20160414101842/http://repository.tamu.edu/bitstream/handle/1969.1/5474/ESL-IC-06-11-312.pdf?sequence=4 |date=2016-04-14 }}. . Retrieved April 19, 2008.</ref>
|style="text-align:left"| Low source temperature
| ''2.4''
| 2.2
| 1.9
| ‐
| ‐
| ‐
|-
|style="text-align:left"| High-efficiency ASHP, air at 0&nbsp;°C<ref name="CREN"/>
|style="text-align:left"| Low output temperature
| ''3.8''
| 2.8
| 2.2
| 2.0
| ‐
| ‐
|-
|style="text-align:left"| Prototype transcritical {{chem|CO|2}} (R744) heat pump with tripartite gas cooler, source at 0&nbsp;°C<ref name="STEEN">SINTEF Energy Research [http://www.r744.com/knowledge/papers/files/pdf/pdf_379.pdf 'Integrated CO<sub>2</sub> Heat Pump Systems for Space Heating and DHW in low-energy and passive houses', J. Steen, Table 3.1, Table 3.3] {{webarchive|url=https://web.archive.org/web/20090318233012/http://www.r744.com/knowledge/papers/files/pdf/pdf_379.pdf |date=2009-03-18 }}. . Retrieved April 19, 2008.</ref>
|style="text-align:left"| High output temperature
| 3.3
| ‐
| ‐
| ''4.2''
| ‐
| 3.0
|-
|style="text-align:left"| Ground-source heat pump (GSHP), water at 0&nbsp;°C<ref name="CREN"/>
|style="text-align:left"|
| 5.0
| 3.7
| 2.9
| 2.4
| ‐
| ‐
|-
|style="text-align:left"| GSHP, ground at 10&nbsp;°C<ref name="CREN"/>
|style="text-align:left"| Low output temperature
| ''7.2''
| 5.0
| 3.7
| 2.9
| 2.4
| ‐
|-
|style="text-align:left"| Theoretical [[Carnot cycle]] limit, source −20&nbsp;°C
|style="text-align:left"|
| 5.6
| 4.9
| 4.4
| 4.0
| 3.7
| 3.4
|-
|style="text-align:left"| Theoretical [[Carnot cycle]] limit, source 0&nbsp;°C
|style="text-align:left"|
| 8.8
| 7.1
| 6.0
| 5.2
| 4.6
| 4.2
|-
|style="text-align:left"| Theoretical [[Transcritical cycle|Lorentzen cycle]] limit ({{chem|CO|2}} pump), return fluid 25&nbsp;°C, source 0&nbsp;°C<ref name="STEEN"/>
|style="text-align:left"|
| 10.1
| 8.8
| 7.9
| 7.1
| 6.5
| 6.1
|-
|style="text-align:left"| Theoretical [[Carnot cycle]] limit, source 10&nbsp;°C
|style="text-align:left"|
| 12.3
| 9.1
| 7.3
| 6.1
| 5.4
| 4.8
|}

===Carbon footprint===
The [[carbon footprint]] of heat pumps depends on their individual efficiency and how electricity is produced. An increasing share of low-carbon energy sources such as wind and solar will lower the impact on the climate.

{| class="wikitable"
|-
! heating system !! emissions of energy source !! efficiency || resulting emissions for thermal energy
|-
| heat pump with onshore wind power || 11&nbsp;g{{CO2}}/kWh<ref>{{Cite web |title=How Wind Can Help Us Breathe Easier |url=https://www.energy.gov/eere/wind/articles/how-wind-can-help-us-breathe-easier |access-date=2023-09-13 |website=Energy.gov |language=en |archive-date=2023-08-28 |archive-url=https://web.archive.org/web/20230828230748/https://www.energy.gov/eere/wind/articles/how-wind-can-help-us-breathe-easier |url-status=live }}</ref>|| 400% (COP=4) || 3&nbsp;g{{CO2}}/kWh
|-
| heat pump with global electricity mix || 436&nbsp;g{{CO2}}/kWh<ref>{{Cite web |date=2023-04-11 |title=Global Electricity Review 2023 |url=https://ember-energy.org/latest-insights/global-electricity-review-2023/ |url-status=live |archive-url=https://web.archive.org/web/20230411233554/https://ember-climate.org/insights/research/global-electricity-review-2023/ |archive-date=2023-04-11 |access-date=2023-09-13 |website=Ember |language=en-US}}</ref> (2022) || 400% (COP=4) || 109&nbsp;g{{CO2}}/kWh
|-
| natural-gas thermal (high efficiency)|| 201&nbsp;g{{CO2}}/kWh<ref name="Quaschning 2022">{{harvnb|Quaschning|2022}}</ref> || 90%{{Cn|date=September 2023}}|| 223&nbsp;g{{CO2}}/kWh
|-
| heat pump<br />electricity by lignite (old power plant)<br />and low performance || 1221&nbsp;g{{CO2}}/kWh<ref name="Quaschning 2022"/> || 300% (COP=3) || 407&nbsp;g{{CO2}}/kWh
|}

In most settings, heat pumps will reduce {{CO2}} emissions compared to heating systems powered by [[fossil fuels]].<ref name="UK sabotaging decarbonize">{{Cite web|title=The UK is sabotaging its own plan to decarbonize heating|url=https://www.engadget.com/air-source-heat-pumps-uk-120044198.html|access-date=2021-06-06|website=Engadget |date=27 May 2021 |archive-date=2021-06-06|archive-url=https://web.archive.org/web/20210606155712/https://www.engadget.com/air-source-heat-pumps-uk-120044198.html|url-status=live}}</ref> In regions accounting for 70% of [[world energy consumption]], the emissions savings of heat pumps compared with a high-efficiency gas boiler are on average above 45% and reach 80% in countries with cleaner electricity mixes.<ref name=ieareport /> These values can be improved by 10 percentage points, respectively, with alternative refrigerants. In the United States, 70% of houses could reduce emissions by installing a heat pump.<ref>{{cite journal |last1=Deetjen |first1=Thomas A |last2=Walsh |first2=Liam |last3=Vaishnav |first3=Parth |journal=Environmental Research Letters |volume=16 |issue=8|title=US residential heat pumps: the private economic potential and its emissions, health, and grid impacts |date=2021-07-28 |page=084024 |doi=10.1088/1748-9326/ac10dc |bibcode=2021ERL....16h4024D |s2cid=236486619 |doi-access=free }}</ref><ref name=ieareport /> The rising share of renewable electricity generation in many countries is set to increase the emissions savings from heat pumps over time.<ref name=ieareport />

Heating systems powered by green hydrogen are also low-carbon and may become competitors, but are much less efficient due to the energy loss associated with hydrogen conversion, transport and use. In addition, not enough green hydrogen is expected to be available before the 2030s or 2040s.<ref>{{Cite web|date=2021-05-21|title=Can the UK rely on hydrogen to save its gas boilers?|url=https://inews.co.uk/news/can-the-uk-rely-on-hydrogen-to-save-its-gas-boilers-1014119|access-date=2021-06-06|website=inews.co.uk |archive-date=2021-06-06|archive-url=https://web.archive.org/web/20210606155711/https://inews.co.uk/news/can-the-uk-rely-on-hydrogen-to-save-its-gas-boilers-1014119|url-status=live}}</ref><ref>IEA (2022), Global Hydrogen Review 2022, IEA, Paris https://www.iea.org/reports/global-hydrogen-review-2022 {{Webarchive|url=https://web.archive.org/web/20230110225147/https://www.iea.org/reports/global-hydrogen-review-2022 |date=2023-01-10 }} , License: CC BY 4.0</ref>