I’ve been thinking again over the past few days about whether we should replace our existing gas boiler with a heat pump earlier than planned. What initially discouraged me was the fact that subsidies (in a reasonable amount) are only available once the gas boiler is at least 20 years old. But well, pointless regulations and laws—a side issue. I am actually very satisfied with having chosen gas in the past. For example, during screed heating, we consumed many kilowatt-hours, and with a heat pump, you would have to use electric heaters for that (seasonal performance factor = 1). Until spring 2022, we mostly paid less than 5 cents, at the end just over 5 cents.
We currently have a fixed contract with a price cap at 9.4 cents for gas and 30.6 cents for electricity. I checked what options we have once this price cap expires:
- 8.2 cents gas
- 31.0 cents electricity
(both again with a 12-month price cap)
This results in an implied seasonal performance factor of 3.78, above which the heat pump would be more efficient. Yes, there are base fees, but on the other hand, the expected lifetime is also a factor. Currently, everyone claims that a heat pump won’t last 30–40 years like gas boilers have long proven in practice.
I used the calculator from the Federal Heat Pump Association for a low-energy house, 35 degrees Celsius (95°F) flow temperature, VWL 75, 40–50 percent domestic hot water share (matching our current consumption—we have 24/7 circulation and want to keep it; on the other hand, the building was built to KfW 55 standard back then, just not officially certified; for example, no solar panels on the roof since we have a well-insulated house as a compensatory measure [monolithic structure, but good windows, good roof insulation, etc.]), 60 degrees Celsius (140°F) storage temperature (also here: 60 degrees is the optimal temperature to prevent Legionella—we won’t save a few cents per day at the expense of our health), and the calculator shows a seasonal performance factor between 3.66 and 3.78.
You could factor in heat pump electricity prices, but then there are shutdown periods, right? That could be problematic with the 24/7 circulation. The electricity price in that case would be 22.3 cents plus a base fee, a second meter, and so on.
22.3 cents / 3.78 = 5.9 cents per kWh heating energy. Okay—so you save about 414 euros per year at 17,000 kWh. Possibly with problems due to shutdown periods and/or the heat pump’s lifespan (+ initial investment of around 20,000).
We currently have a fixed contract with a price cap at 9.4 cents for gas and 30.6 cents for electricity. I checked what options we have once this price cap expires:
- 8.2 cents gas
- 31.0 cents electricity
(both again with a 12-month price cap)
This results in an implied seasonal performance factor of 3.78, above which the heat pump would be more efficient. Yes, there are base fees, but on the other hand, the expected lifetime is also a factor. Currently, everyone claims that a heat pump won’t last 30–40 years like gas boilers have long proven in practice.
I used the calculator from the Federal Heat Pump Association for a low-energy house, 35 degrees Celsius (95°F) flow temperature, VWL 75, 40–50 percent domestic hot water share (matching our current consumption—we have 24/7 circulation and want to keep it; on the other hand, the building was built to KfW 55 standard back then, just not officially certified; for example, no solar panels on the roof since we have a well-insulated house as a compensatory measure [monolithic structure, but good windows, good roof insulation, etc.]), 60 degrees Celsius (140°F) storage temperature (also here: 60 degrees is the optimal temperature to prevent Legionella—we won’t save a few cents per day at the expense of our health), and the calculator shows a seasonal performance factor between 3.66 and 3.78.
You could factor in heat pump electricity prices, but then there are shutdown periods, right? That could be problematic with the 24/7 circulation. The electricity price in that case would be 22.3 cents plus a base fee, a second meter, and so on.
22.3 cents / 3.78 = 5.9 cents per kWh heating energy. Okay—so you save about 414 euros per year at 17,000 kWh. Possibly with problems due to shutdown periods and/or the heat pump’s lifespan (+ initial investment of around 20,000).
And it could also be recommended, as long as the gas heating system is still working, to experiment with flow temperatures and heating settings to see how low you can go, even with a gas heating system. And in a private home, I would actually always recommend looking into photovoltaic systems despite the "winter lull."
andimann schrieb:
Hi,
what you are doing right now is deliberately making the heat pump look bad. At which point?
You will only know what was right in 10-20 years. I’m currently considering something similar; we built with a gas heating system 8 years ago and I’m thinking about replacing the gas heating prematurely. It should already add up now with the current parameters. Otherwise, you can always react later.
Installing a heat pump now will very likely protect you from having to switch to district heating later. Once the mayors and municipal utilities realize that with mandatory connections they can generate almost unlimited prices and profits and award lucrative contracts to their associates, there will be a huge gold rush. Just connecting to district heating in a few years will cost about the same as a heat pump today. Digging up the garden and laying pipes is expensive. After that, you are completely at the mercy of the district heating operators’ pricing. According to current legal interpretation, mandatory connection for a heat pump cannot be enforced. And according to legal interpretation in xyz years, it might be different again.
If you wait until your gas heating breaks down, you will have a big problem getting a heat pump at a reasonable price on short notice. This will end with you installing another gas heating system, which you then have to replace with a heat pump after 3 years. That makes even less sense. You would have the same problem if your heat pump fails. I don’t see people installing a gas heating system short-term only to switch back to a heat pump after 3-4 years. Also, by common understanding, heat pumps have a significantly shorter lifespan than gas heating systems, which often last 30-40 years in existing buildings.
A heat pump also does not cost the 20-30k€ that Dahlbomii mentions. I have a completed offer here for 24k€, of which 40% funding is deducted, leaving 14.4k€. If I also factor in that I can skip the planned upgrade of an air conditioning system (just a minimal version in the living room) thanks to the heat pump’s cooling function, I end up at about 10k€ in costs. (Yes, that’s optimistic calculation...). And in the worst case, the heating lasts 15 years until 2039, your gas heating would have lasted until 2045, and due to declining demand, the ratio will stay at 1:4 or even lower until then. And according to your earlier argument, you would then have to install a gas heating again on short notice in 2039 and a new heat pump in 2042.
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