Product List

Selection Criteria Electric Water Heaters

Methodology (Best products of Europe) presents the most energy efficient heat pump water heaters.


There are many different systems to supply domestic hot water (combined with space-heating, separate water heaters with a storage tank or instantaneous water heaters). The energy used varies from oil or gas boilers, to electrical resistance heaters or (electrical) air source heat pumps, to renewable sources like solar collectors, wood or industrial waste heat (often combined with space-heating as backup in winter and with electrical heaters in summer).

Heat pump water heaters are much more energy efficient than electrical resistance heaters, because they use electric heat pumps to extract heat from the surrounding air or from outside. The air source must not be from a heated room, since this would steal energy from the heating system. In Europe, every third domestic water heater is an electrical resistance heater. Around 4 million units electric water heaters are sold per year.

The most sustainable way of supplying domestic hot water is by using renewable energy like solar radiation. For some countries, solar water heating systems are presented on their Topten-site.

Technical criteria

All heat pump water heaters presented under meet the following criteria:

  • Certified according to the FWS Quality Label in Switzerland.
  • COP (Coefficient of performance)
    • Air temperature 15°C: ≥ 2.9 (see note below)
    • Air temperature 7°C: ≥ 2.9
    • Air temperature 20°C: ≥ 3.2
  • Measured according EN 16147: 2011

Note: The water heater list on is until further notice identical with the list of (Switzerland). Due to running rebate programmes for heat pump water heaters in Switzerland (ProKilowatt) the list on is based on the COP at 15°C.

However, in the EU an energy label for water heaters enters into force by the end of September 2015. It will be based on measurements at a temperature of 20°C and not anymore of 15°C as done up to now and also used in Switzerland for the rebate programmes. Topten will observe the market and introduce new selection criteria for as soon as possible.

Data Sources

  • Manufacturers and suppliers
  • Performance data must be proven by a test report (e.g. Prüfresultate WPZ)

Order of presentation

The products are ranked by the COP. The order of presentation can be changed by clicking on the headings of the tables.


Brand, Model, Other models

Brand with link to website. Certified model for which the test report is provided. Similar models by the same brand that are also certified.

Volume in litres

Electric heating in kW

An additional electric heating element allows the water to heat up at about twice the speed and to higher temeratures than by operating with the heat pump only. The temperature is normally set to 65°C.

Additional heat exchanger

Here, the boiler can be connected for fast heating and for covering peaks in hot water demand. Another option is to connect solar collectors.

Air duct

Air ducts allow to supply (and conduct) the air from outside or the next room. The supplied air serves as heat source and cools down in the process.

COP Coefficient of performance

The COP describes the ratio of heat in tapped hot water to consumption of electricity. Higher COP value means better performance. Tested according to EN 16147:2011.

Load profile

EN 16147 gives a choice of five load profiles (S, M, L, XL and XXL) under which the COP can be tested.

Ambient temperature storage tank

Ambient temperature storage tank in °C. Both test standards give the following choice of test conditions for the COP test: 15°C for indoor air, 20°C for outdoor air and exhaust air.

Temperatures source / water

Temperature of heat source (air), temperatures of cold inlet water and hot water in °C. The test standards prescribe the temperature of air and cold inlet water as in the following table. The hot water temperature is a test result.

EN 16147:2011

Temperature of heat source:
Outdoor air
Indoor air
Exhaust air


Temperature of cold inlet water 10°C


  • Sound power level indoors in dB(A)


Standards and Labels

  • EHPA European Heat Pump Association, Brussels
  • FWS Fachvereinigung Wärmepumpen Schweiz, Switzerland


  • The european council for an energy efficient economy eceee provides a status overview on all products in the Ecodesign & Energy Labelling process
  • Coolproducts informs about the EU ecodesign process on water heaters and other products. It is a coalition of NGOs' campaign for a stronger, fast Ecodesign Directive to save the climate and money.

Producers and suppliers are kindly asked to contact info(at) to register products which meet the Topten selection criteria.

07/2016 Josephy/Nipkow