COMPARATIVE CALCULATION DRAWN UP BY ENERGY CONSULTANT AND HEATING ENGINEER KARL PETER MAYER FROM AROSA IN SWITZERLAND.
With the demand to use renewable energies and the so-called energy revolution, there is a major shift away from fossil fuelled heating systems. Everyone is now only talking about heat pumps or heating systems in heating networks. This overlooks the fact that there are other heating systems that are also powered by renewable energies, but whose acquisition costs are a fraction of those of a heat pump. Furthermore, no technical specialists are required to carry out expensive installations. This heating system is an electric storage heater with a storage core – not to be confused with night storage heater!
The following is an example of a comparative calculation between an air/water heat pump and a comparable system with decentralised electric storage heaters from Thermotec AG.
The air/water heat pump is used in many places, although its cost-effectiveness is not very high. Particularly in very periods, the heat pump becomes a purely electric heating system. The lower air temperature in winter can mean that homes no longer get warm.
The customer is not told that additional electric heating coils are installed in the air/water heat pumps, which cause the often high electricity consumption. Our example now refers to an air/water heat pump for a heating system with conventional radiators.
The electrical performance data and the investment of the heat pump:
Split heat pump at +7 °C a heating output of 7.7 KW (55 °C VL). Electrical power consumption:
Outdoor unit 5.81 KW
Indoor unit 1.38 KW
Total 7.19 KW
An electric heating element is installed in the heat pump, which can be operated with 2, 4 or 6 KW. In order to achieve the 55 °C flow temperature to the radiator when the outside tem-perature is below +7 °C, this must be switched on. The more below-zero temperatures, the more additional electrical energy is required. In higher regions, you have to assume 6 KW.
We assume 4 KW per hour for our calculations
above +7 °C 7.19 KW
below +7 °C 11.19 KW
Investment and maintenance:
To calculate the operating hours, we refer to the standard. For heating systems without domestic hot water, this states 1300 full utilisation hours as the calculation basis.
Investment costs:
Split heat pump in Switzerland approx. 7 KW | € 21’813.– |
Installation and removal in the heating system | € 18’000.– |
Gesamt | € 39’814.– |
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Electricity and maintenance costs:
Electricity costs per year for (1300 h)
2 months above 7 °C | € 1’336.– |
1.5 months below 7 °C | € 1’802.– |
Annual maintenance | € 350.- |
Total | € 3’488.– |
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Electric storage heater from Thermotec
It is important to use the right quality when choosing an electric heater. Conventional ra-diators only have heating wires inside, which have poor heat transfer and therefore poor efficiency. Thermotec radiators have a storage heating core on the inside and fins on the out-side for better heat convection. They therefore do not require a fan. The heat distribution is the same as with conventional hot water radiators.
Investment costs for 8 KW heating output.
8 radiators and material | € 5’800.– |
Installation | € 2’000.– |
Total | € 7’800.– |
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Electricity costs for 1300 hours of full use
Electricity costs per year at 1300 hours | € 2’600.– |
Total | € 2’600.– |
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Our balance sheet
Comparison of total costs
Air/water heat pump | Thermotec electric heating | |
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Investment | € 39’814.– | € 7’800.– |
Subsidy | € 3’000.– | € 0.– |
A difference of € 31’013.-
Comparison of total costs
Air/water heat pump | Thermotec electric heating | |
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Electricity + maintenance | € 3’488.– | € 2’600.– |
Capital costs 5 %/year | € 1’841.– | € 390.– |
Depreciation: 20 years | € 1’990.– | € 260.– |
Total costs /yearly | € 7’318.– | € 3’250.– |
A yearly difference of € 4’068.-
Summary
- The air/water heat pump does not pay for itself at any time. There are (example) approx. € 4000.- additional costs per year.
- In addition to the costs for the heat pump, there are also costs for a domestic hot water generator.
- The so called ‘grey costs’ for the overall construction (production, transport, installation, storage, etc.) are significantly lower with partial storage heating.
- Simple installation through wall mounting with plug-in 220 volt.
- The availability of materials and manpower is currently better for electric storage heaters than for heat pumps.
- Programming (night setback, etc.) and an app can actively optimize the electricity costs of electric storage heaters.

