Hello everyone!
A quick question:
Why do people actually add solar thermal systems to their gas heating?
Is it because they have to comply with the energy saving regulations?
Wrong, you are allowed to skip solar thermal if other measures reduce energy consumption by at least 15%.
Example:
I’m planning a KfW-55 house with gas heating, solar thermal, controlled ventilation with heat recovery, and excellent insulation.
Now I remove the solar thermal system. What happens?
I lose the KfW-55 status and end up with KfW-70, so I lose a €2,500 subsidy. But I save €6,000 by not installing solar thermal. The operating costs increase by €50 per year due to the missing solar thermal, which adds up to €1,000 over 20 years. So overall, I still save €2,500.
Savings:
€6,000 saved by not installing solar thermal*
- €2,500 lost KfW-55 subsidy
- €1,000 higher operating costs due to no solar thermal*
=======
€2,500
Sounds like an attractive alternative, or is there a major calculation mistake somewhere?
The whole calculation would also apply to a KfW-85 house, which would qualify as a KfW-100 house without the solar thermal.
Best regards
jx7
PS:
Please don’t bring up heat pumps or pellet heating; this is not meant to start a fundamental debate about gas versus heat pumps (with sharp increases in energy prices, heat pumps will eventually become more cost-effective). The initial question is simply: "If using gas, then maybe without solar thermal?"
* Source: xxx-Heizungsvergleich-de "Gas + 5sqm solar thermal"
A quick question:
Why do people actually add solar thermal systems to their gas heating?
Is it because they have to comply with the energy saving regulations?
Wrong, you are allowed to skip solar thermal if other measures reduce energy consumption by at least 15%.
Example:
I’m planning a KfW-55 house with gas heating, solar thermal, controlled ventilation with heat recovery, and excellent insulation.
Now I remove the solar thermal system. What happens?
I lose the KfW-55 status and end up with KfW-70, so I lose a €2,500 subsidy. But I save €6,000 by not installing solar thermal. The operating costs increase by €50 per year due to the missing solar thermal, which adds up to €1,000 over 20 years. So overall, I still save €2,500.
Savings:
€6,000 saved by not installing solar thermal*
- €2,500 lost KfW-55 subsidy
- €1,000 higher operating costs due to no solar thermal*
=======
€2,500
Sounds like an attractive alternative, or is there a major calculation mistake somewhere?
The whole calculation would also apply to a KfW-85 house, which would qualify as a KfW-100 house without the solar thermal.
Best regards
jx7
PS:
Please don’t bring up heat pumps or pellet heating; this is not meant to start a fundamental debate about gas versus heat pumps (with sharp increases in energy prices, heat pumps will eventually become more cost-effective). The initial question is simply: "If using gas, then maybe without solar thermal?"
* Source: xxx-Heizungsvergleich-de "Gas + 5sqm solar thermal"
L
Lebensprojekt12 Aug 2015 21:19jx7 schrieb:
Hello everyone!
A quick question:
Why do people actually add solar thermal systems to their gas heating?
Is it because they have to comply with the energy saving regulations?
Wrong, you are allowed to skip solar thermal as long as other measures reduce energy demand by 15% below the regulation.
Example:
I am planning a KfW-55 house with gas heating, solar thermal system, controlled mechanical ventilation with heat recovery, and excellent insulation.
Now I remove the solar thermal system. What happens?
I lose the KfW-55 status and drop to KfW-70, so I forfeit a subsidy of €2,500. On the other hand, I save €6,000 from omitting the solar thermal system. The running costs increase by €50 per year due to the missing solar thermal system, which adds up to €1,000 over 20 years. So overall, I still save €2,500.
Savings:
€6,000 saved by omitting solar thermal*
- €2,500 lost KfW-55 subsidy
- €1,000 higher operating costs due to omitting solar thermal*
=======
€2,500 total savings
Sounds like an appealing alternative, or is there a major calculation error somewhere?
The same calculation works with a KfW-85 house, which without solar thermal still qualifies as a KfW-100 house.
Best regards,
jx7
PS:
Please don’t start with heat pumps or pellets, this is not meant to trigger a fundamental discussion about gas versus heat pumps (with drastic energy price increases, heat pumps will eventually be more cost-effective). The question here is only: “If using gas, then possibly without solar thermal?”.
* Source: xxx-Heating-comparison-de “Gas + 5sqm solar thermal”Hello,
Although this thread is from early March, I would be interested to know how you plan to achieve KfW 55 with a gas heating system? Also, did you actually manage to reach KfW 55?
Regards
No, I haven’t achieved this myself, but I believe I read that it is possible. If not, then the example was poorly chosen.
However, I still think that the option of gas heating without solar thermal (using alternative measures to meet the relevant standards) is discussed far too little, because the investment costs for solar thermal systems are quite high.
In my opinion, it could be more cost-effective in some cases either to save the money on solar thermal entirely and cover the higher heating costs with those savings, or to invest the saved money in better insulation, which might reduce heating costs more effectively than solar thermal.
However, I still think that the option of gas heating without solar thermal (using alternative measures to meet the relevant standards) is discussed far too little, because the investment costs for solar thermal systems are quite high.
In my opinion, it could be more cost-effective in some cases either to save the money on solar thermal entirely and cover the higher heating costs with those savings, or to invest the saved money in better insulation, which might reduce heating costs more effectively than solar thermal.
S
sonnenkind809 Sep 2015 15:47I share the same opinion and implement it accordingly (even though I haven’t calculated down to the last cent). I will install a gas-only heating system without a heat storage tank or similar. However, I am not using any KfW subsidies, so meeting the KfW thresholds is not a priority for me, as they don’t provide any indication of the actual heating costs at the end of the year.
E
ErikErdgas5 Oct 2015 11:57Hello building expert,
does your comment refer generally to the use of solar thermal systems to support heat generation, or is it specifically related to the example? Of course, the use of solar thermal heating and domestic hot water production depends on many factors in each individual case, but it should not be fundamentally ruled out that they can contribute more or less significantly to meeting the demand.
Best regards, Erik
does your comment refer generally to the use of solar thermal systems to support heat generation, or is it specifically related to the example? Of course, the use of solar thermal heating and domestic hot water production depends on many factors in each individual case, but it should not be fundamentally ruled out that they can contribute more or less significantly to meeting the demand.
Best regards, Erik
B
Bauexperte5 Oct 2015 14:05Hello Erik,
In that respect, for my clients who wanted to stick with gas as their heat source, I have always recommended the 15% rule in the past – after April 16 it looks different, and I am curious to see what solutions the conventional gas industry will offer.
Regards, Bauexperte
ErikErdgas schrieb:From my #16? Yes, I mean it in general.
Is your comment generally referring to the use of solar thermal systems for heat generation support, or is it specifically related to the example?
ErikErdgas schrieb:More on the lesser side, and mostly theoretical on paper. A bit of solar for domestic hot water heating has, in my opinion, allowed conventional heating installers to participate in the “renewable energy” scene. Or it has helped simple sales promoters position their package deals in the market; everyone knows the “good” gas.
Of course, the use of solar thermal heating and domestic hot water systems depends on many factors in each individual case, but the fact that they can contribute to coverage to a greater or lesser extent should not be fundamentally ruled out.
In that respect, for my clients who wanted to stick with gas as their heat source, I have always recommended the 15% rule in the past – after April 16 it looks different, and I am curious to see what solutions the conventional gas industry will offer.
Regards, Bauexperte
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