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.
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.
The annual performance factor (seasonal performance factor) of a well-adjusted and properly sized brine-to-water heat pump should be at least 4.5, even for horizontal ground collectors. For this, the entire system including the heat source must be correctly sized and planned.
We installed our trench collector ourselves for under 3,000 euros.
A geological and hydrogeological report as well as extensive reading in the pink forum are essential! You will also need a good builder or similar. It is definitely not the easiest path.
Solar thermal requires large storage tanks to buffer all the heated water until demand arises. A heat pump needs small storage tanks to minimize energy loss in hot water production. In winter, the solar thermal system either does not work or works poorly, so the heat pump has to heat the large storage tank.
Better to use photovoltaic panels, as you can do more with them...
We installed our trench collector ourselves for under 3,000 euros.
A geological and hydrogeological report as well as extensive reading in the pink forum are essential! You will also need a good builder or similar. It is definitely not the easiest path.
Becker84 schrieb:
Why is it advised against to operate a heat pump together with solar thermal??
Solar thermal requires large storage tanks to buffer all the heated water until demand arises. A heat pump needs small storage tanks to minimize energy loss in hot water production. In winter, the solar thermal system either does not work or works poorly, so the heat pump has to heat the large storage tank.
Better to use photovoltaic panels, as you can do more with them...
We have a compact unit with 180 liters (48 gallons) of hot water heated to 45°C (113°F). So, 20 minutes of showering is no problem... Filling the bathtub and then showering afterward works fine as well – the heating element is turned off.
However, it depends on the showerhead – just a simple calculation: 9 liters per minute at 40°C (104°F) would mean about 22 minutes for us – it’s unclear whether water flows in during that time, but probably not much.
If you have a rainforest shower with 22 liters (6 gallons) per minute, then the maximum time is about 10 minutes.
But honestly, there’s no harm in buying a 300-liter (79 gallons) hot water tank as well; the heat loss of tanks is not very high – you just have to decide if you really need that capacity.
However, it depends on the showerhead – just a simple calculation: 9 liters per minute at 40°C (104°F) would mean about 22 minutes for us – it’s unclear whether water flows in during that time, but probably not much.
If you have a rainforest shower with 22 liters (6 gallons) per minute, then the maximum time is about 10 minutes.
But honestly, there’s no harm in buying a 300-liter (79 gallons) hot water tank as well; the heat loss of tanks is not very high – you just have to decide if you really need that capacity.
...and do you have a deep borehole?
I am considering the Junkers Supraeco T STM 120-2 (3–12 kW) with 190 liters (50 gallons) of hot water.
I used to think that a heat pump could never manage to adequately reheat hot water without an electric heating element. With our gas boiler, you can tell the difference, and it heats the water at flow temperatures well above 65°C (149°F)... although it doesn’t display this unfortunately.
At my parents’ house, I believe it was nearly 100°C (212°F).
I am considering the Junkers Supraeco T STM 120-2 (3–12 kW) with 190 liters (50 gallons) of hot water.
I used to think that a heat pump could never manage to adequately reheat hot water without an electric heating element. With our gas boiler, you can tell the difference, and it heats the water at flow temperatures well above 65°C (149°F)... although it doesn’t display this unfortunately.
At my parents’ house, I believe it was nearly 100°C (212°F).
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