Reading the energy label of a heat pump water heater: ηwh, load profile and annual consumption

The energy label of a heat pump water heater looks like that of other appliances, but its figures mean something different from those of a heat pump for heating. This guide walks through the parts so you can compare labels of different models fairly.

What is on the label?

The label for water heaters follows Regulation (EU) No 812/2013. Since 26 September 2017 it has used the scale A+ to F ¹. A heat pump water heater label shows:

• the energy class for water heating, with the declared load profile;
• the annual electricity consumption, for an average, a colder and a warmer climate;
• the sound power indoors and, for units with an outdoor part, outdoors;
• a separate symbol for appliances that only work during off-peak hours ¹.

The same data is in the product information sheet in EPREL, which also lists the efficiency per climate. One example: a heat pump water heater with load profile XL, class A+, ηwh 129%, annual consumption of 1,298 kWh and sound power of 52 dB indoors and 49 dB outdoors ².

ηwh: why it can exceed 100%

Water heating efficiency ηwh is the ratio of useful energy to the energy needed to generate it, expressed as a percentage ¹. For electricity, the regulation applies a conversion coefficient of 2.5 to arrive at primary energy ¹. A heat pump water heater that gets well over 2.5 kWh of heat from 1 kWh of electricity therefore scores above 100%. An ordinary electric boiler turns 1 kWh of electricity into 1 kWh of heat and stays far below that value.

Efficiency differs per climate. The EPREL example gives 119% for a colder, 129% for an average and 153% for a warmer climate ². The average climate is the standard reference and the value we show as the headline figure.

The load profile: a test pattern, not a household size

The load profile (3XS, XXS, XS, S, M, L, XL, XXL, 3XL, 4XL) describes how much hot water is drawn during the test. The test lasts 24 hours: nothing is drawn until 07:00, after which the draw-offs of the profile follow ¹. The manufacturer may declare the largest profile the appliance can meet, or the one just below it ¹.

The regulation does not link profiles to household sizes. For your choice this means: check the datasheet for how much hot water the appliance delivers per day, and use the profile mainly to compare labels with each other.

Compare only within the same profile

The class limits differ per load profile. In the regulation the limit for class A+++ is ηwh ≥ 62 for 3XS and ηwh ≥ 163 for M ¹. A higher efficiency at a larger profile therefore does not automatically mean a better appliance. The category page also has selections per load profile, in which only models with the same profile stand side by side.

Annual consumption: mind the rounding

Annual consumption in the register is often given in whole gigajoules. We convert it to kWh (1 GJ is 277.8 kWh), so the values are roughly rounded. Use annual consumption as a guideline and compare it with the consumption of your current boiler.

Smart control and off-peak operation

Some appliances only run during off-peak hours or have smart control. With smart control, the values on the label may only apply when that control is switched on; the regulation has this recorded in the product information sheet ¹. This matters most if you have a dynamic energy contract or want to use your own solar power.

Checklist

1. Choose a load profile that fits your hot-water use.
2. Compare ηwh and annual consumption only within the same profile.
3. Use the average climate as the reference.
4. Check the indoor sound level if the unit goes in a living space.
5. Look up the registration number in EPREL if you want to verify a value.
6. Ask for tank volume, heating-up time and electrical power in the datasheet.