A hot water heat pump – often called a heat pump boiler – exclusively heats the domestic hot water, not the heating. For this, it mostly uses the heat of the ambient air, for example in the cellar, and works significantly more economically than a pure electric boiler. This makes it an affordable entry into heat pump technology, especially if the heating is not yet to be replaced. Combined with solar electricity, it becomes particularly attractive. (As of: July 2026)
Key points in brief
- The hot water heat pump only heats the domestic hot water, the heating remains unaffected.
- It mostly uses the heat of the ambient air and needs significantly less electricity for it than an electric boiler.
- It is an affordable, minimally invasive entry – sensible when an old electric boiler is replaced.
- It can be well combined with solar electricity: it runs at midday when the system delivers.
- It does not replace a heating renewal – for that, a heating heat pump is needed.
What is a hot water heat pump?
A heat pump that limits itself to a single task: the hot water. Instead of warming the whole house like a heating heat pump, it only heats the domestic hot water in the boiler – i.e. the water for shower, bath and kitchen. That is why it is often simply called a heat pump boiler.
The principle is the same as with any heat pump: it extracts heat from the environment and raises it to a usable level. Mostly it uses the air in the installation room for this – often a cellar or technical room, where there is some heat anyway. As a result, it needs significantly less electricity for the same amount of hot water than a classic electric boiler, which heats the water directly with a heating element.
This clearly distinguishes it from the large solution: the heating heat pump warms the whole house and is part of a heating replacement. The hot water heat pump leaves the existing heating untouched and only takes care of a sub-area. This makes it a small entry.
For whom is the entry worthwhile?
Especially for households that want or have to replace an old electric boiler without immediately touching the whole heating. Exactly in this constellation, the hot water heat pump plays to its strengths.
A pure electric boiler is one of the most inefficient ways to heat water – it converts electricity directly into heat, one to one. A hot water heat pump gets a multiple of heat from the same amount of electricity, because it draws the largest part of the energy from the ambient air. Anyone who has an aged electric boiler noticeably lowers their electricity consumption for hot water with the switch.
It is particularly sensible if the heating is still running well and a complete heating replacement is not imminent. Then the hot water heat pump is a manageable step with clear benefit, which does not turn the whole house upside down. If, on the other hand, a heating replacement is imminent anyway, the hot water is usually included in the planning of the large heat pump right away – then no separate solution is needed.
A point from practice: the hot water heat pump slightly cools the room from which it draws the heat. In a cellar this is mostly unproblematic or even desirable. However, it needs a suitable installation room with enough air volume – that is part of the planning.
How does it interact with a solar system?
Exceptionally well – hot water is one of the most grateful consumers for solar electricity. The reason is the timing: the hot water heat pump can be easily controlled so that it runs at midday, when the solar system delivers a lot.
Hot water is an ideal «battery» for surplus solar electricity, because the boiler holds the heat for hours. Instead of feeding the midday surplus into the grid at the low tariff, you heat the water for the evening with it. This lines up exactly with the levers described in the article on optimising self-consumption: placing a large consumer in the sun hours. The boiler thus becomes the «cheapest battery that is already in the cellar», as the article on battery and heat pump formulates it.
For many households, the combination of solar system and hot water heat pump is therefore an effective duo – with manageable effort and without the heating having to be touched.
The hot water heat pump is often the underestimated solution. If someone comes to us with a solar system and the heating is still running flawlessly, the old electric boiler is frequently the biggest unnecessary power guzzler in the house. Replacing it with a heat pump boiler is a small intervention with noticeable effect – and the midday electricity from the roof lands directly in the warm water. What we pay attention to is the installation room: the boiler needs air from which it draws the heat. In a normal cellar this is no problem. In a small, tight room you have to look more closely.
Frequently asked questions
Does a hot water heat pump replace the heating?
No. It only heats the domestic hot water, the heating remains unaffected. Anyone who wants to replace the heating needs a heating heat pump. The hot water heat pump is the partial step for one area – ideal if the heating is still running and only the boiler is due.
Is the switch from the electric boiler worthwhile?
In many cases yes, because an electric boiler heats the water directly with electricity very inefficiently. A hot water heat pump needs significantly less electricity for the same amount of hot water, because it gets the largest part of the energy from the ambient air. Especially in combination with a solar system, the benefit is great.
Will the cellar become cold due to the hot water heat pump?
It slightly cools the installation room, because it extracts heat from it. In a normal cellar this is mostly unproblematic. Important is a room with sufficient air volume; a very small, tight room is less suitable. The assessment of the installation location is part of the planning.
Can I run the hot water heat pump specifically with solar electricity?
Yes, and that is one of its biggest advantages. It can be controlled so that it preferably runs at midday when the solar system produces a lot. The boiler retains the heat for hours so that the water heated with solar electricity is available in the evening. This way, the surplus is used instead of feeding it in cheaply.
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Swissolar member and Solarprofi · ESTI installation authorisation (Art. 14 NIV) · in Zurich since 2017 · over 150 systems completed · a personal answer from the specialist company, no call centre
Sources: General technical fundamentals of hot water heat pumps (heat pump boilers) and their operation with solar electricity; empirical values from the planning practice of ecoEn GmbH, Zurich region.
Last updated: 9 July 2026 · Author: ecoEn editorial team
