Definitions of terms used across this site. Where a term has a regulatory source (EN 14825, F-gas regulation, EPREL), it is referenced.
Instantaneous ratio of useful heating output to electrical energy input, measured at one specific test condition (e.g. A7/W35 = outdoor 7°C, water 35°C). A COP of 4.0 means 4 kWh of heat per 1 kWh of electricity. Always read alongside the test point — COP at A7 differs sharply from COP at A-7.
See also: scop, seer, test-points
Annual-average COP weighted across realistic operating conditions in a defined climate zone, per EN 14825. Single most useful number for comparing heat pumps. Computed for three EU climate zones: Average (Strasbourg), Warmer (Athens), Colder (Helsinki).
See also: cop, climate-zones, en-14825
Cooling-mode equivalent of SCOP — annual-average ratio of cooling output to electrical input. Reported by reversible (heating + cooling) heat pumps and air conditioners.
Eurodesign-equivalent of SCOP, expressed as a percentage relative to a reference (193 % at 35°C low-temperature, 144 % at 55°C medium-temperature for Average climate). Used in EU energy labels.
See also: scop, energy-class
Standardized operating conditions used to measure COP. Air-water heat pumps use codes like A-7/W35 (outdoor air -7°C, supply water 35°C). Lower outdoor and higher water temperatures both depress COP.
Periodic reverse cycle to clear frost from the outdoor coil during humid sub-zero conditions. Costs energy and depresses real-world SCOP, especially around 0–5°C.
See also: scop, test-points
COP is a single-condition snapshot useful for technical comparison; SCOP integrates over a whole heating season and matches what households actually experience over a year. Use SCOP for purchase decisions, COP curves for sizing.
Heat pump that extracts heat from outdoor air and delivers it via a water-based circuit (radiators, underfloor heating, hot-water cylinder). Most common residential type in Europe; cheapest to install but COP drops at very low outdoor temperatures.
See also: ground-source-hp, monobloc, split
Extracts heat from the ground via buried collector loops (horizontal field) or vertical boreholes. More stable and higher COP than air-source because soil temperature varies less. Higher capex due to ground works.
See also: air-water-hp, borehole
All refrigerant circuit is sealed inside a single outdoor unit; only water (and electricity) goes into the home. Easier and faster to install — no F-gas-licensed installer required for the refrigerant connection.
Refrigerant flows between an outdoor unit and an indoor heat exchanger. More flexible siting but requires F-gas-certified installer to connect the refrigerant lines.
Combines a heat pump with a backup gas boiler. The system optimises which to use based on outdoor temperature and tariff. Lower investment than full HP retrofit but keeps fossil dependency.
See also: air-water-hp
Hot water for showers, washing, kitchen use — distinct from space heating. Heat pumps handle DHW either through a buffer cylinder or with a dedicated DHW heat pump.
See also: buffer-tank
Insulated water cylinder that decouples HP cycling from heat demand and supplies DHW or radiator water. Sized 30–80 L per kW for buffering, 200–500 L for DHW.
See also: dhw
System designed to run with supply water ≤ 35°C — typically underfloor heating. Heat pumps achieve much higher COP at low supply temperatures (often 4–5+) than at 55°C+.
See also: high-temp-application, scop
System designed to run with supply water around 55–65°C — typically existing radiator systems. Heat pumps need higher capacity and accept lower COP in this regime.
See also: low-temp-application
Working fluid of the heat-pump cycle that evaporates and condenses to move heat. Choice affects efficiency, GWP and flammability. Modern HPs increasingly use R32 or R290.
Multiplier comparing a refrigerant's climate impact to CO₂ over a 100-year horizon. R290 propane: 0. R32: 771. R410A: 1924. EU F-gas regulation drives down allowed GWP year by year.
See also: f-gas, refrigerant
Refrigerant's relative impact on the ozone layer. All modern refrigerants (HFC, HFO, natural) have ODP = 0; only legacy CFC and HCFC types had positive ODP.
See also: refrigerant
ISO 817 class for mildly flammable refrigerants (e.g. R32, R454C). Requires basic mitigation (charge limits, sensors) but generally safe for residential use. A3 (R290 propane) is highly flammable and tightly charge-limited.
See also: refrigerant
Letter grade A+++ to G shown on EU energy labels. For space heaters the scale was rebalanced in 2019; modern heat pumps typically score A++ or A+++.
EU regulation 2024/573 progressively phasing down high-GWP fluorinated refrigerants. New residential HPs ≤ 12 kW must use refrigerants with GWP ≤ 150 from 2027; ≤ 50 from 2032 in many cases.
See also: gwp
European Product Database for Energy Labelling. Mandatory registry for any product placed on the EU market with an energy label. Public API exposes model parameters; manufacturers are responsible for accuracy.
See also: energy-class, eu-2017-1369
European standard defining test conditions and computation method for SCOP and ηs. Specifies the three climate zones (Average, Warmer, Colder) used in EU energy labels and EPREL registrations.
See also: scop, climate-zones
Energy Labelling Framework Regulation — the umbrella law mandating product registration in EPREL and standardised energy labels.
See also: eprel
EU framework setting minimum efficiency requirements for energy-related products. For heat pumps, Regulation 813/2013 sets minimum ηs values that products must meet to be sold legally.
See also: energy-class
UK Microgeneration Certification Scheme. Required for installations to qualify for UK subsidies (Boiler Upgrade Scheme). Both products and installers must be MCS-certified.
France's 'Reconnu Garant de l'Environnement' label for installers. Required to access MaPrimeRénov' grants and other French eco-renovation aids.
See also: mcs-certification
EN 14825 splits the EU into Warmer (Athens reference), Average (Strasbourg) and Colder (Helsinki). SCOP must be reported for the matching zone in each EPREL registration.
Sum over the year of (base − daily mean temperature) for days where the mean is below the base (commonly 18°C or 18.3°C). Higher = colder. A useful proxy for annual heating demand.
See also: cdd, climate-zones
Mirror of HDD, summed over days with mean temperature above the base. Indicates cooling demand for reversible heat-pump usage.
See also: hdd
Coldest typical winter temperature used to size a heating system. Local building codes set values (e.g. -10°C for central Germany, -25°C for northern Sweden). Heat pumps must meet load at this temperature.
See also: test-points
Consumption category 2 500–4 999 kWh/yr — typical single-family electricity user in EU. Eurostat publishes prices per band semi-annually under dataset nrg_pc_204.
See also: eurostat
Statistical office of the EU. Source of household and industrial energy tariffs, energy mix data and environmental indicators used across this site.
See also: household-band-dc
Total: 34 terms. We're extending this glossary regularly — corrections welcome via the address on the About page.