How does a domestic hot water heat pump work and what are its advantages?

 In Geothermal Heat Pump, Geothermal Source Heat Pump, Ground Source Heat Pump, Heat pump, Heating, Rewatemp, sanitary water heat pump, Shallow Geothermal Energy, Sustainability, water water heat pump

A water heater or domestic hot water heat pump (DHW heat pump) is one of those often overlooked yet crucial pieces of equipment that provides everyday comfort.


We take warm water for granted. We open the tap and the water is hot in a few seconds. We forget about the equipment that enables this luxury – except in two cases:

  • When there is no hot water and we notice something is wrong.
  • When we receive the electricity bill and remember that our old water heater really consumes a lot of power. This is especially true for larger buildings such as kindergartens, schools, hotels and wellness centres – where less efficient heating devices have a huge impact on costs.

We’d all prefer to look at the monthly electricity bill and be pleasantly surprised at how little energy we’ve spent heating water. That’s why we’re going to talk about a device which can help you with that – a heat pump for domestic hot water.

In a four-member household, we consume 200 to 250 litres of hot water per day, which is a significant amount that has a big impact on costs. The amount of water in larger buildings (hotels, companies etc.) is of course significantly larger and its impact on costs as well.

Therefore, it is important to know all the heating options and a domestic hot water heat pump is definitely a green, efficient and economical solution.

Let’s look at what you need to pay attention to when considering purchasing it – especially when it comes to larger buildings.

1.) How does a domestic hot water heat pump work?
2.) Advantages of a domestic hot water heat pump

How does a domestic hot water heat pump work?

First of all, it is necessary to know that the heat pump for domestic hot water heats only sanitary water  – only domestic hot water (for washbasins, showers, toilet bowls), while the heat pump heats the whole building. This is the main difference between these devices.

A simplified explanation of a domestic hot water heat pump operation is as follows: 

Sanitary water heat pumps use electricity to generate heat using heat energy from the environment. This saves up to 70% of energy and can be significantly more efficient and economical than conventional heaters.

The pump operates in the opposite way to conventional refrigerators. It takes heat energy from the surrounding air, increases the temperature by compression and thus heats the water in the water tank. It also returns cooler air to its surroundings.

As a result of this process, you must pay attention to the following factors when using a domestic hot water heat pump:

  • The space in which it operates must be large enough. At least 30 cubic meters is recommended.
  • The pump will cool this space, so consider the purpose of the space.
  • Such pumps are more efficient in warm climates or in rooms where there is an element that heats the surroundings (eg a stove for other purposes). In these cases, they can draw more heat from the air.
  • The pump can use outdoor or indoor air – you can take advantage of that during hot summers.
  • Pumps are not efficient in colder climates. In this case, it is better to look for an alternative.

A sanitary heat pump can also use shallow geothermal energy sources. You can read more about how heat pumps use geothermal resources in our article on this topic.

Geothermal energy is more efficient than the use of air, as its source has a more constant temperature.

An important advantage is also the possibility of using a desuperheater if you already use a geothermal heat pump to heat your building.

A desuperheater is a small heat exchanger that uses hot gases produced by a heat pump compressor during its operation. Is uses the gases to heat the domestic hot water at a higher temperature regime. Desuperheater can also operate without a water storage tank and only heat the water when needed.

In summer, when the heat produces a lot of excess heat, you can heat all the necessary amount of water this way.

You can connect the domestic hot water heat pump to an existing domestic hot water tank or order a specialized container, which often allows even better energy efficiency, as it is tailor-made for use with a heat pump.


Advantages of a domestic hot water heat pump

A heat pump for domestic hot water (DHW heat pump) has many advantages over other methods of heating water (gas, wood, other energy sources). Let’s see what to expect:

Low water heating costs and a quick return on investment

The cost of purchasing and installing a domestic hot water heat pump is higher than most alternatives, but it pays off quickly – presumably in 5 to 7 years.

Such water heating is up to 75% cheaper than usual. If a 4-member household pays € 100 per month for water heating, this means up to € 75 in savings each month. For larger buildings, the savings are, of course, even higher.

You can also receive an eco subsidy for the heat pump, which reduces the initial costs and ensures that the investment pays off even faster.

When it comes to efficiency, we should also mention the COP factor (Coefficient of performance), which speaks of the ratio between the obtained thermal energy and the invested electricity.

The higher the EF, the more efficient the water heater. Efficient gas water heating has an EF of 0.65. A SW heat pump has EF 2.0. You can see that the difference in efficiency is considerable.


It harnesses green energy

The heat pump for sanitary water reduces environmentally harmful carbon dioxide emissions by up to 60%. It uses renewable energy sources. Not only is it environmentally friendly, it is also not dangerous as it does not use fuels that could harm you.


Reliable and easy to use

A suitable model of a DHW heat pump never runs out of an energy source. The energy of the earth’s crust, air or groundwater is always available. Replacement due to an unsuitable energy source is almost never necessary.

Also, these types of pumps do not require much maintenance, and their use is simple and user-friendly. This means that you will have little work to do with the heat pump and it will not cause you any worries.


DHW heat pump –  great choice even for smaller buildings

The heat pump for domestic hot water has an important spatial advantage – it does not need an energy storage device, as it draws energy from the environment. Therefore, it takes up very little space and is an excellent choice for smaller facilities, such as cottages, weekends, etc. It can be mounted directly on the wall, which is an added bonus for smaller buildings.

If it is a house that you only use in the summer, you can even install the pump so that it will heat the water and help you air-condition the room at the same time, as it cools its surroundings by taking heat from the air.

Now you see why you should consider using a domestic hot water heat pump and what energy sources are available to you. This concludes our series of five articles on shallow geothermal energy and the possibilities of its use. 

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