ᐅ Gas or heat pump in a KfW55 energy-efficient house

Created on: 17 May 2016 23:08
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Becker84
Hello, I am currently trying to evaluate the advantages of gas versus electricity.

I’m assuming an annual demand of 5000 kWh including hot water.
What is a realistic seasonal performance factor (SPF) for 2 deep boreholes or for collectors just a few meters underground?

Heat pump costs around €310 for 1500 kWh => SPF 3.3
I have concerns about heat pumps regarding hot water production, as the efficiency is likely to be low when there is a temperature difference of 40-60°C (104-140°F). This is likely to reduce the overall seasonal performance factor, even though the SPF for underfloor heating at 25-30°C (77-86°F) can be above 4.5.
Is anyone’s practical experience available on this?

Gas costs are almost exactly the same at €310.

Purchase costs for gas:
- Gas boiler with solar and hot water 3000-5000 € ?
- Gas connection ? ?

Purchase costs for heat pump:
- Heat pump with hot water storage tank approximately 6000 € ?
- Deep borehole including installation 10,000 € ?
- Or ground collectors ? ?

+ BAFA subsidy 4500 €

Does it make sense to buy a separate air-source heat pump for hot water that is located inside the house and therefore has to heat from approximately 20°C (68°F) to 60°C (140°F)?
Or would it be better to purchase a heat pump with an integrated hot water tank and a solar connection, similar to a gas boiler?

If the operating costs (without photovoltaic system) are roughly the same, I would tend to choose the heat pump, since photovoltaic would allow additional savings in the future.
G
Goldi09111
19 May 2016 22:15
I'm really not sure if the additional investment in a heat pump compared to gas will ever pay off. Which parameters should you base the calculation on? No one knows what gas or electricity prices will be in the future...
S
Saruss
19 May 2016 22:31
The better a house is insulated, the less important the heating system becomes – you can save a higher percentage on very low heating costs, but in absolute terms the savings are minimal. Aside from that, gas is not available everywhere. For the environment, a heat pump (preferably geothermal) combined with solar power is probably the best option.

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