September 27, 2023, 12:42 pm | Read time: 3 minutes
Heat pumps promise climate-friendly heating, efficiency, and even receive subsidies. A test now shows: They can all heat, but that’s not all that matters.
The Stiftung Warentest evaluated six air-to-water heat pumps in heating mode for efficiency and environmental properties. The result: All the heat pumps tested can heat a typical single-family home.
These Are the Winners of Stiftung Warentest
Efficiency in terms of energy performance and environmental properties in heating mode accounted for 70 percent of the overall score. The winning pump from Viessmann (model Vitocal 250-A AWO-E-AC 251.A10) was rated “Good” (grade 2.1) in this category. It is very economical with both radiator and underfloor heating.
The Wolf CHA-10/400V received an efficiency score of 2.2. It is slightly less efficient with radiator heating than the Viessmann pump, but also very efficient with underfloor heating.
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The Choice of Refrigerant
Both heat pumps impressed Stiftung Warentest with a low annual climate impact—due to electricity consumption and choice of refrigerant. They also use the comparatively climate-friendly refrigerant propane (R290), according to Stiftung Warentest.
R290 is considered a “natural refrigerant,” with three times the greenhouse effect of CO2. The refrigerant R454C, used in the third-place Stiebel Eltron WPL-A 07 HK 230 Premium, is significantly less climate-friendly. According to the testers, it has 148 times the greenhouse effect.
The potentially climate-damaging refrigerant R32 has 675 times the greenhouse effect of CO2—two devices in the test field use it. Stiftung Warentest experts find the use of R32 “unnecessary,” as the two top-ranked devices achieved better energy efficiency results with propane.
The better insulated a house is, the larger the area heat pumps can heat. On average, the six tested heat pumps can heat 2,454 square feet (228 square meters) with good insulation, 1,475 square feet (137 square meters) with moderate insulation, and 1,001 square feet (93 square meters) with poor insulation, according to the testers—good insulation allows for more than double the area compared to poor insulation.
Solid Overall Result
In the overall assessment by Stiftung Warentest, the heat pumps from the three German manufacturers performed best: The Viessmann pump, as the test winner, received an overall score of 2.1, the model from Wolf a 2.3, and the pump from Stiebel Eltron an overall score of 2.4.
In addition to another good pump, two models were rated “Satisfactory” overall—a solid result overall.
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Calculating Costs
In the test field, the cheapest model cost 9,050 euros, the most expensive 19,400 euros. However, total costs depend not only on the list price of the devices but also on installation costs and available subsidies—up to 30,000 euros in subsidies are possible.
The testers also advise checking with the electricity provider to see if there is a cheaper electricity tariff for heat pumps.
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Other Criteria
Noise development also played a role in the overall test result. All test devices, except one, scored “Good” in this regard. However, the operation of an air-to-water heat pump can be disturbing, especially at night.
Experts therefore recommend clarifying before installation how far the pump must be from neighboring properties and what requirements there are regarding its orientation. Quieter operating modes reduce noise by throttling the fan, but this also means lower efficiency.
In terms of handling (installation, commissioning, instructions, and app), all six devices received good to very good ratings. Data protection was consistently rated only as “Satisfactory.”