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"
A fireplace is also planned, but we haven’t looked into specific models or efficiency ratings yet, since it is primarily intended for coziness. It’s interesting to know there are additional factors to consider.
What I’m curious about is whether I am correctly interpreting the option with controlled ventilation/heat recovery.
What I’m curious about is whether I am correctly interpreting the option with controlled ventilation/heat recovery.
T21150 schrieb:
Hi,
the answer is probably: No!
For our KFW70 house with a gas condensing boiler, we needed both controlled ventilation with heat recovery and solar thermal for domestic hot water. This was already required under the 2009 energy saving regulations because of the coverage rate for renewable energies.Yes, the options will also be calculated by experts. Although it is now 2016, the old energy saving regulations still apply to us, since we submitted our application in December. In addition, we do not want to achieve the KFW standard but only want to reduce the minimum requirements by 15% through an alternative measure in order to avoid solar thermal. A better building envelope was the first option – then I came across the issue of controlled ventilation with heat recovery.
Best regards
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