Heat pumps at Warentest – German devices are ahead

Heating technology
Heat pumps at Warentest – German devices are ahead

The heat pump is the only heating system that increases the energy used.

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Heat pumps are on everyone’s lips. The product testers examined six air heat pumps. The devices from Viessmann and Wolf are particularly efficient and use a climate-friendly refrigerant.

Hardly any other device has been discussed more this year than the heat pump. A reason for Stiftung Warentest to take a look at these devices. A complex test because the machines are relatively expensive. But the product testers were not deterred by this. They didn’t rely on the manufacturer’s information, but measured themselves. Of the six models tested, four performed well. The heat pump from Viessmann was able to place right at the top. The pumps from Daikin and Mitsubishi only perform satisfactorily. A heat pump with the appropriate indoor unit, which brings the energy from the pump into the heating circuit, was evaluated. And that has an additional electric heating element.

Well-known operating principle

Despite the great debate, heat pumps are still a mystery to many. The principle is very simple and well-known: the refrigerator and air conditioning work according to the same system. Energy is transported through compression and decompression of a refrigerant. You can experience the basic idea with an air pump; the compression causes it to heat up noticeably during operation. There is only one paradox that troubles common sense. The heat pump turns cold into cozy warmth because it can extract energy from the outside air at just 10 degrees and thus generate over 55 degrees on the other side.

The foundation only tested air-water heat pumps; this technology is the most commonly used in Germany. The installation is also much easier than with pumps that extract their energy from the groundwater. The test structure is realistic, but does not cover every individual situation. The key word in the test is energy efficiency. What does that mean? Strictly speaking, a heat pump is an extremely efficient electric heater. Electricity is required for their operation, the fans and the movement of the refrigerant. But the heat pump increases the energy. The more energy the heat pump can extract from the outside air with one kilowatt of electricity, the more efficient it is. The testers measured this. In practice, there are always deviations because the devices react differently to the outside temperatures. The question of how hot the heating water should be also has an impact.

Model house of 140 square meters

All models tested can heat a single-family home and can also be used to retrofit an existing house, although “with limitations,” as the testers write. The efficiency of the pump determines its operating costs: the more efficient it is, the less electricity you have to buy to heat the house. The calculation was based on a moderately insulated house with 140 square meters of living space. The test winner requires 5,000 kilowatt hours per year, the worst-placed device requires 1,500 kilowatt hours more. Over the years, this negates the cheaper purchase price. It also becomes clear that the heat pump is more attractive when electricity prices are low than when they are high. Some pumps still use the refrigerant R32 – it can harm the climate. But only if it escapes, which normally shouldn’t happen. In addition to the power consumption, the volume is important because the pump fans can be heard. This constant background noise can be dampened by cleverly positioning the pumps, but in any case, distances from neighbors must be maintained.

The device from Viessmann (Vitocal 250-A AWO-E-AC 251.A10) takes first place; it costs 18,700 euros and requires 4,950 kilowatt hours per year for the model house. Number two is the Wolf CHA-10/400V. Both devices use climate-neutral propane as a refrigerant. In most areas of Germany you can also operate them with a radiator heater. In very cold zones it should be underfloor heating.

Complicated cost accounting

The product testers indicate the list price of the devices. In reality, the “real price” is more complicated. In any case, the installation costs will be added to the device. It’s not just working hours, the electricity connection, cables and a base also need to be paid for. On the other hand, many devices on the market are much cheaper than in the list. On top of that, there are subsidies that make the system significantly cheaper for the customer.

The test contains further information on the subject of “heat pumps”. Anyone interested should take a close look at it. The efficiency of each pump depends heavily on how well the house is insulated, what type of heating is used and what the ambient temperature is at the location. Simply put: A pump that is ideal for a well-insulated new building with underfloor heating does not have to be the best choice for a moderately insulated existing building with radiators.

You can take the entire test for a fee here see.

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