Hello everyone,
some background on my questions:
I am currently exploring the possibility of converting our house from a gas heating system to a heat pump. It might sound completely crazy for a house that is just under 7 years old, but this could be funded and financed as an “energy renovation project” together with a photovoltaic system through KFW 261. That could actually make it economically very attractive.
I am still in the evaluation phase and have started initial discussions with heating and solar experts.
This immediately raised some questions for me, because the first offers are quite contradictory to the principles I often see discussed here in the forum:
The insulation level of the house is about KFW 55 standard; however, the overall standard was not met back then due to the gas heating system. The heating demand is around 12,000-13,000 kWh for a total of 270 square meters (2,900 square feet). There is underfloor heating throughout, including the basement.
Best regards,
Andreas
some background on my questions:
I am currently exploring the possibility of converting our house from a gas heating system to a heat pump. It might sound completely crazy for a house that is just under 7 years old, but this could be funded and financed as an “energy renovation project” together with a photovoltaic system through KFW 261. That could actually make it economically very attractive.
I am still in the evaluation phase and have started initial discussions with heating and solar experts.
This immediately raised some questions for me, because the first offers are quite contradictory to the principles I often see discussed here in the forum:
- Buffer tank (heating water) – Question: What exactly is the purpose of this and when does it make sense? So far, no seller has been able to clearly answer this, although the technical answer is simple: it should act as a hysteresis to reduce short cycling of the heat pump. The general idea is understandable, but I don’t really see how 100 liters (35 gallons) of buffer tank help when just the volume of my underfloor heating system already exceeds 200 liters (70 gallons), plus the large mass of screed acting as thermal storage. The current gas heating system works fine without a heating buffer tank.
- Heat pump capacity and modulation – the first quotes naturally come with absurdly oversized heat pumps because they only consider the total heated area of 270 square meters (2,900 square feet). When I point out that 12 or even 16 kW seems excessive, the answer is always: “It can modulate down from 3 to 12 kW.” That’s fine, but exactly this modulation is often warned against. So question: why is modulating down performance considered a problem? Is this the short cycling that people warn about? Technically, modulation means the entire system, including the compressor and all components, runs slower. But then the question arises how efficient it still is.
The insulation level of the house is about KFW 55 standard; however, the overall standard was not met back then due to the gas heating system. The heating demand is around 12,000-13,000 kWh for a total of 270 square meters (2,900 square feet). There is underfloor heating throughout, including the basement.
Best regards,
Andreas
Did you find out more about direct marketing at EnBW? Can you share any details?
Otherwise, try reaching out to a smaller consultant; sometimes they still put in the effort to prepare everything so the bank has minimal work and know which banks will handle it.
I think it will definitely be difficult below 50,000 (about 54,000) though. Maybe build a garden shed and put photovoltaic panels on it as well? A larger battery storage system to increase the costs?
Otherwise, try reaching out to a smaller consultant; sometimes they still put in the effort to prepare everything so the bank has minimal work and know which banks will handle it.
I think it will definitely be difficult below 50,000 (about 54,000) though. Maybe build a garden shed and put photovoltaic panels on it as well? A larger battery storage system to increase the costs?
Hello,
I checked out Lumenza. They specialize in direct marketing of small systems. Whether it will actually work out that way remains to be seen.
Hmm. Artificially inflating the costs to exceed 50,000 (currency) probably doesn’t make much sense in the end. We already have a 10 kWh battery storage system planned; I can’t fully drain it during summer or fully charge it during winter. Yes, we could fill the carport with more panels, but that would just increase costs without much additional benefit. And then the return on investment wouldn’t be that great either.
Of course, I can still consult the energy advisor, and tomorrow I’ll push myself to visit some local bank branches in person. But without 0.24% financing, it probably won’t work out; paying out of pocket isn’t enjoyable, and the whole thing would just end up burning money.
What a pity... so close to the goal...
Best regards,
Andreas
I checked out Lumenza. They specialize in direct marketing of small systems. Whether it will actually work out that way remains to be seen.
Hmm. Artificially inflating the costs to exceed 50,000 (currency) probably doesn’t make much sense in the end. We already have a 10 kWh battery storage system planned; I can’t fully drain it during summer or fully charge it during winter. Yes, we could fill the carport with more panels, but that would just increase costs without much additional benefit. And then the return on investment wouldn’t be that great either.
Of course, I can still consult the energy advisor, and tomorrow I’ll push myself to visit some local bank branches in person. But without 0.24% financing, it probably won’t work out; paying out of pocket isn’t enjoyable, and the whole thing would just end up burning money.
What a pity... so close to the goal...
Best regards,
Andreas
What? No! Definitely fill the entire carport! The marginal cost for each additional module decreases. You can feed in more (store more), etc. Since the fixed costs for installation only occur once, it’s beneficial to spread them over more kWp.
Okay, there are some step-related costs. If you exceed certain limits, you might need a larger or a second inverter, etc. So you have to make sure you’re just over those thresholds, but otherwise, more modules generally means more benefits.
You’re right about the battery; you don’t need a larger one. But if you have to exceed 50,000 EUR, that’s a different matter...
You’re not that far off. If it has to be 75,000 EUR, okay, that might be a bit too much. But I think 50,000 EUR should be achievable somewhere.
Okay, there are some step-related costs. If you exceed certain limits, you might need a larger or a second inverter, etc. So you have to make sure you’re just over those thresholds, but otherwise, more modules generally means more benefits.
You’re right about the battery; you don’t need a larger one. But if you have to exceed 50,000 EUR, that’s a different matter...
You’re not that far off. If it has to be 75,000 EUR, okay, that might be a bit too much. But I think 50,000 EUR should be achievable somewhere.
andimann schrieb:
Hello,
I checked out Lumenza. They specialize in direct marketing of small systems. Whether it really works out that way remains to be seen.
Hmm. Artificially driving the costs up to exceed 50k probably doesn’t make much sense in the end. We already have a 10 kWh battery planned; I can’t fully use it in summer or fully charge it in winter. Yes, we could fully load the carport, but that would just generate more costs without much added value. And then the ROI wouldn’t be all that great either.
Of course, I can still ask the energy consultant, and tomorrow I’ll push myself to visit a few local bank branches again. But without 0.24% financing, it’s unlikely to work out; paying out of pocket isn’t fun, and then the whole project just ends up burning money.
What a mess… so close to the goal…
Best regards,
Andreas Just take the heat pump offer for 42k and voilà, your photovoltaic system will be well over 50k 🙂
What do you mean by “paying out of pocket isn’t fun” — financing at market interest rates or paying entirely from your own funds?
Hello,
In the end, it amounts to the same thing. Whether I finance the money or withdraw it from my stock portfolio, in both cases I have to factor in about 4% interest. By the way, this is almost always overlooked in economic calculations for photovoltaic systems. It’s as if the money simply falls from the sky.
And when you have to consider 4% on the invested capital, the ROI for the combination of heat pump and photovoltaic easily shifts to 20 years or more. By then, the heat pump will already need replacing. That would really only be a hobby project, for a clear conscience, or to be independent from gas. In other words, it’s not only a break-even but you are expected to lose money over time. That’s what I mean by “paying out of pocket.”
Photovoltaics alone still work; you can make the numbers look good even with your own capital. The ROI is somewhere around 13-15 years, and these systems are supposed to last significantly longer than that.
With the KFW loan, your overall renovation measures result in an ROI of 12 years without having to break into your savings first. In other words, it’s not only good for the environment but also economically viable.
Best regards,
Andreas
leschaf schrieb:
"Paying out of pocket isn’t fun" – financing at market interest rates or paying entirely with your own funds?
In the end, it amounts to the same thing. Whether I finance the money or withdraw it from my stock portfolio, in both cases I have to factor in about 4% interest. By the way, this is almost always overlooked in economic calculations for photovoltaic systems. It’s as if the money simply falls from the sky.
And when you have to consider 4% on the invested capital, the ROI for the combination of heat pump and photovoltaic easily shifts to 20 years or more. By then, the heat pump will already need replacing. That would really only be a hobby project, for a clear conscience, or to be independent from gas. In other words, it’s not only a break-even but you are expected to lose money over time. That’s what I mean by “paying out of pocket.”
Photovoltaics alone still work; you can make the numbers look good even with your own capital. The ROI is somewhere around 13-15 years, and these systems are supposed to last significantly longer than that.
With the KFW loan, your overall renovation measures result in an ROI of 12 years without having to break into your savings first. In other words, it’s not only good for the environment but also economically viable.
Best regards,
Andreas
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