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.
N
nordanney19 May 2016 11:48The brine heat pump handles it easily. For us, 500 liters (132 gallons) at 48 degrees Celsius (118°F) (large family, domestic hot water station).
N
nordanney19 May 2016 14:11Becker84 schrieb:
45°C (113°F) for 15-20 minutes is sufficient for me... But what about Legionella? They also like it nice and warm *g* This is not an issue with our storage tank because it is a fresh water station. This means that the water in the (separate) tank heats fresh water via plate heat exchangers. So the tank’s water never comes into contact with the potable water.
nordanney schrieb:
The brine heat pump manages this easily. For us, 500 liters (132 gallons) at 48 degrees Celsius (118°F) (large family, fresh water station).But purely that is more than enough. You can already slightly burn your skin at 48 degrees Celsius (118°F).
When I, as someone who tends to feel cold, see on my phone that the hot water tank is at 37–38 degrees Celsius (99–100°F) near the top, I can still comfortably shower with it for 20 more minutes.
I save a lot on hot water in winter (typical Swabian, meaning extremely cost-conscious) – the temperature in the tank often drops considerably. Hot water is heated once a day, to 55 degrees Celsius (131°F). That has to be enough. For a spontaneous full bath (large tub), there is the useful "one-time charge" function...
Every four weeks, however, I perform thermal disinfection to make life difficult for Legionella bacteria. This uses about 1.5 cubic meters (53 cubic feet) of gas, roughly 16 kWh; the boiler is heated to 80 degrees Celsius (176°F) and then all hot water pipes are flushed with it. In summer this is not necessary, as the clever solar system heats the boiler enough that you could power locomotives with steam...
I assume, without direct experience, that with a heat pump you also have to carry out thermal disinfection, but then using an electric heating element. Because maintaining 40–48 degrees Celsius (104–118°F) constantly really does pose a risk of Legionella.
Best regards,
Thorsten
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