ᐅ Semi-detached house from 2008 – gas heating system malfunctioning – what to decide?
Created on: 22 Sep 2025 22:02
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Max1809Hello everyone,
We live in the south of Germany in a semi-detached house built in 2008 with 110 m² (1,184 sq ft) of living space. We bought the house last year.
The house has a Vitodens 200 gas boiler (condensing) with a 100-liter (26-gallon) hot water storage tank Vitocell 100 in the attic. The gas heating system has caused us problems from the start because, according to the previous owner, the "heat exchanger is clogged," which was also confirmed by the local heating technician. The purchase price was negotiated down accordingly. The gas boiler cycles very frequently (runs for about 30 seconds, reaches 60°C (140°F), then switches off, repeating this every 10 minutes), so it cannot deliver heat efficiently. We also hear recurring noises in the radiators, either from lime scale coming off or pressure fluctuations. There is also a loss of pressure, so I have to top up the system every four weeks. The gas boiler is from 2008.
[ATTACH type="full" width="718px"]92962[/ATTACH]
However, the house is very well insulated, with 60 cm (24 inches) of brick wall including built-in insulation. The windows are double-glazed. Our annual heating and hot water consumption is 9,000–9,500 kWh. We are currently a two-person household, and we consider this very good. The supply temperature rarely reaches 50°C (122°F). I can share the heating curve from the app if needed.
Now to the main question: What would be the smartest way to fix the situation with the somewhat problematic heating system? I must say that except for the mentioned issues, the boiler heats the house perfectly. However, the high cycling frequency worries me. According to the ViCare app, the boiler has already had 740,000 burner starts and a total burner operating time of 14,000 hours.
The options currently on the table:
1. Install a new heat exchanger for 2,000 euros material costs and 600 euros installation costs.
2. Completely replace the gas boiler (again a Vitodens 200 or 100) (hopefully I can keep the existing flue system, which would cost around 7,000–8,000 euros).
3. Switch directly to a heat pump: we have an offer for 38,000 euros (a 30% subsidy is possible but not the 20% one because the gas boiler is not yet 20 years old).
From a purely economic perspective, I see it this way:
Running costs (assuming electricity at $0.30/kWh and gas at $0.11/kWh, including maintenance):
- Gas boiler: about $1,230 per year
- Heat pump:
- SPF 3.0 → about $1,125
- SPF 3.2 → about $1,070
- SPF 3.5 → about $990
Savings with a heat pump compared to a new gas boiler: $100–240 per year depending on efficiency. Even with rising gas prices, they would have to increase significantly for a heat pump to pay off within about 20 years.
Payback period (investment difference of about 19,000 euros between the heat pump and gas boiler):
- At SPF 3.0: ~180 years
- At SPF 3.2: ~115 years
- At SPF 3.5: ~80 years
What is your opinion? Which option would you tend to choose?
At the moment, we honestly lean towards a new heat exchanger, even though it feels a bit like "beating a dead horse" to invest in a nearly 20-year-old gas boiler. But maybe it will still last well for another 6–7 years until it reaches 25 years of service, by which time we might have more funds available and heat pumps may be more advanced and cheaper.
Thank you very much for your opinions! We are torn and sorry if I left out anything important. I’m happy to provide more details!
Best regards,
Max
We live in the south of Germany in a semi-detached house built in 2008 with 110 m² (1,184 sq ft) of living space. We bought the house last year.
The house has a Vitodens 200 gas boiler (condensing) with a 100-liter (26-gallon) hot water storage tank Vitocell 100 in the attic. The gas heating system has caused us problems from the start because, according to the previous owner, the "heat exchanger is clogged," which was also confirmed by the local heating technician. The purchase price was negotiated down accordingly. The gas boiler cycles very frequently (runs for about 30 seconds, reaches 60°C (140°F), then switches off, repeating this every 10 minutes), so it cannot deliver heat efficiently. We also hear recurring noises in the radiators, either from lime scale coming off or pressure fluctuations. There is also a loss of pressure, so I have to top up the system every four weeks. The gas boiler is from 2008.
[ATTACH type="full" width="718px"]92962[/ATTACH]
However, the house is very well insulated, with 60 cm (24 inches) of brick wall including built-in insulation. The windows are double-glazed. Our annual heating and hot water consumption is 9,000–9,500 kWh. We are currently a two-person household, and we consider this very good. The supply temperature rarely reaches 50°C (122°F). I can share the heating curve from the app if needed.
Now to the main question: What would be the smartest way to fix the situation with the somewhat problematic heating system? I must say that except for the mentioned issues, the boiler heats the house perfectly. However, the high cycling frequency worries me. According to the ViCare app, the boiler has already had 740,000 burner starts and a total burner operating time of 14,000 hours.
The options currently on the table:
1. Install a new heat exchanger for 2,000 euros material costs and 600 euros installation costs.
2. Completely replace the gas boiler (again a Vitodens 200 or 100) (hopefully I can keep the existing flue system, which would cost around 7,000–8,000 euros).
3. Switch directly to a heat pump: we have an offer for 38,000 euros (a 30% subsidy is possible but not the 20% one because the gas boiler is not yet 20 years old).
From a purely economic perspective, I see it this way:
Running costs (assuming electricity at $0.30/kWh and gas at $0.11/kWh, including maintenance):
- Gas boiler: about $1,230 per year
- Heat pump:
- SPF 3.0 → about $1,125
- SPF 3.2 → about $1,070
- SPF 3.5 → about $990
Savings with a heat pump compared to a new gas boiler: $100–240 per year depending on efficiency. Even with rising gas prices, they would have to increase significantly for a heat pump to pay off within about 20 years.
Payback period (investment difference of about 19,000 euros between the heat pump and gas boiler):
- At SPF 3.0: ~180 years
- At SPF 3.2: ~115 years
- At SPF 3.5: ~80 years
What is your opinion? Which option would you tend to choose?
At the moment, we honestly lean towards a new heat exchanger, even though it feels a bit like "beating a dead horse" to invest in a nearly 20-year-old gas boiler. But maybe it will still last well for another 6–7 years until it reaches 25 years of service, by which time we might have more funds available and heat pumps may be more advanced and cheaper.
Thank you very much for your opinions! We are torn and sorry if I left out anything important. I’m happy to provide more details!
Best regards,
Max
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nordanney22 Sep 2025 22:16Personal opinion. Repair it and enjoy the gas heating for another 10 years.
The downside is that the heating unit is located in the attic, which makes switching to a heat pump more difficult. I would take my time planning so that you can later switch to a heat pump (outdoor unit on the roof or exterior wall). Aside from that, the price you mentioned is extremely high. It’s way too expensive for a basic replacement, even with some construction challenges.
The downside is that the heating unit is located in the attic, which makes switching to a heat pump more difficult. I would take my time planning so that you can later switch to a heat pump (outdoor unit on the roof or exterior wall). Aside from that, the price you mentioned is extremely high. It’s way too expensive for a basic replacement, even with some construction challenges.
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wiltshire22 Sep 2025 22:28I would have the unit repaired like @nordanney suggested and only consider a heat pump if it is beyond repair or if gas prices skyrocket.
Hello,
I agree with the previous comments: I would have it repaired and push it beyond the 20-year mark, hoping that the increased subsidy is still available then (although that is rather doubtful).
The price for the heat pump is completely absurd. Check the real prices for the materials online (from large, reputable suppliers). Without knowing your offer, I dare to say that the materials would cost well under €15,000 (around $16,000) delivered to your site. If the heating contractor wants to pay more, that’s fine, but they should cover the difference themselves.
That implies labor costs of about €23,000 (around $24,500). If two people work on your heating system for 1 week (which is already quite generous), that equals 80 hours. So about €290 (around $310) per hour — I find that a bit excessive.
The very high subsidies in Germany are primarily a cash cow for all heat pump installers — they no longer reflect the real costs. Unfortunately, this will only improve when the subsidies are completely stopped. Then the same will happen as with electric cars — prices will miraculously drop overnight.
Best regards,
Andreas
I agree with the previous comments: I would have it repaired and push it beyond the 20-year mark, hoping that the increased subsidy is still available then (although that is rather doubtful).
The price for the heat pump is completely absurd. Check the real prices for the materials online (from large, reputable suppliers). Without knowing your offer, I dare to say that the materials would cost well under €15,000 (around $16,000) delivered to your site. If the heating contractor wants to pay more, that’s fine, but they should cover the difference themselves.
That implies labor costs of about €23,000 (around $24,500). If two people work on your heating system for 1 week (which is already quite generous), that equals 80 hours. So about €290 (around $310) per hour — I find that a bit excessive.
The very high subsidies in Germany are primarily a cash cow for all heat pump installers — they no longer reflect the real costs. Unfortunately, this will only improve when the subsidies are completely stopped. Then the same will happen as with electric cars — prices will miraculously drop overnight.
Best regards,
Andreas
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ajokr202523 Sep 2025 19:56andimann schrieb:
The price for the heat pump is completely absurd,No, it isn’t. The government aims to support manufacturers and trade companies to prevent the industry from being fully dominated by Chinese companies, as has already happened with photovoltaics, and is foreseeable with electric vehicles as well. However, it cannot directly subsidize the companies because that would be illegal state aid. So, the funds go to the end customers and, through their payments, to the manufacturers and installers. After all, we are not in China, which we often accuse of state subsidies.Besides labor hours, the installer also has to cover office expenses including staff, vehicles and their contents, as well as preparing quotes for jobs that are never commissioned. They also need to train their employees on the new technology. Manufacturers face similar challenges.
By the way, I would first only replace the heat exchanger and flush the pipes. Possibly install a magnetite separator if none is present and refill only with softened water. At the same time, have a heat meter installed so you know how much of the burned kWh are lost through the chimney. This loss will be avoided with the heat pump in the future.
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