Selection Criteria Electric Water Heaters

Methodology

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

Scope

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 www.topten.eu meet the following criteria:

Energy class A+
Measured according EN 16147: 2011

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Data Sources

Manufacturers and suppliers

Order of presentation

The products are ranked by the eta value. The order of presentation can be changed.

Glossary

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

Volume of the water heater

Electric heating in kW

An additional electric heating element allows the water to heat up at about twice the speed and to higher temperatures 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. Take a look at the table here.

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.