Heat pump water heater or heat pump: what is the difference and when do you choose which?

A heat pump water heater and a heat pump for heating use the same technology, but they solve different problems. One produces hot tap water, the other heats the whole home. That difference decides how you judge them, how you compare them and when each one fits.

What does a heat pump water heater do?

A heat pump water heater has one job: heating tap water for the shower, basin and kitchen. The unit sits on or next to a storage tank, takes heat from ambient air and keeps hot water ready until you need it. Depending on the type, it draws that heat from the room it stands in, from outside air or from ventilation air. For units with an outdoor part, the energy label therefore lists sound power both indoors and outdoors ¹.

European rules decide how such an appliance is rated. The energy label for water heaters, hot water storage tanks and packages is set out in Regulation (EU) No 812/2013, which covers water heaters up to 70 kW and storage tanks up to 500 litres ¹.

How does it differ from an ordinary heat pump?

Combination heaters that both heat the home and make hot water fall outside the water heater regulation and have their own label for heating appliances ¹. A heat pump for heating can supply hot water if you connect a cylinder, but the performance of that combination is not what a heat pump water heater label shows.

How do you read the figures?

Water heating efficiency ηwh shows how much useful heat you get relative to the energy needed. It converts electricity to primary energy with a factor of 2.5 ¹. That is why a good heat pump water heater can exceed 100%, while an ordinary electric boiler stays far below. The EPREL example shows it: a unit with load profile XL reaches 129% in an average climate, 119% in a colder and 153% in a warmer climate ².

The load profile shows how much hot water the manufacturer declared for the label, from very little (3XS) to a lot (4XL). Compare ηwh and annual consumption only within the same profile. More detail is in our guide to the energy label of a heat pump water heater.

When do you choose which?

• You are replacing an electric boiler or a gas water heater and have no heat pump for heating: a heat pump water heater is the logical step.
• You already have a heat pump for heating: first check whether it can feed a hot-water cylinder. That is often the simplest and most efficient route.
• You want to heat your home: then you need a heat pump for heating, not a heat pump water heater.
• You have little space or a cold utility room: look at the sound level and at where the unit takes its heat from.

What our pages show (and what they do not)

Our data comes from the European product register for energy labels (EPREL). It lists water heating efficiency, energy class, load profile, annual consumption and sound. Tank volume, heating-up time and electrical power are not in that register, so check the manufacturer’s datasheet before you buy. On the category page you can filter models and put them side by side.

Common misunderstandings

• An efficiency above 100% is impossible. It is possible, because ηwh is calculated against primary energy.
• A larger load profile means a better appliance. The profile says something about declared use, not about quality. Large profiles often reach higher efficiencies without the appliance being better.
• The energy label tells you everything. The label gives neither tank volume nor heating-up time, and both matter just as much for daily comfort.

Checklist for your choice

1. Know which job you need: tap water only, or heating as well.
2. Pick a load profile that fits your daily hot-water use.
3. Compare ηwh and annual consumption within the same profile.
4. Check the indoor sound level, especially if the unit stands in a living space.
5. Ask for tank volume, heating-up time and connections in the datasheet.