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"
Hello Björn! Well, if the solar thermal system had only cost €3000 (about $3300), you could have almost covered the full amount with the €2500 (about $2750) KfW incentive. The remaining €500 (about $550) would have been quickly recovered through the free hot water supply. But okay, you mentioned that it was mainly for aesthetic reasons.
D
DerBjoern5 Mar 2015 10:13Yep, the main reason was aesthetic. Financially, it wouldn’t have made much sense either, since with KfW55 we would have had to pay an additional surveyor to verify the KfW compliance, which we didn’t need to do with KfW70. These extra costs would have almost completely offset the €2500 grant.
jx7 schrieb:
...the remaining 500 € could be quickly covered by the free hot water supply.....Quickly? You can even generate hot water with gas for a long time using that...
jx7 schrieb:
Incorrect, it is also allowed without solar thermal systems if other measures reduce the energy saving ordinance requirements by 15%.Of course, you can also build using other energy-saving methods. Although you skipped solar this time, you installed your high-performance insulation instead. But that also costs money to achieve KfW 70 standards. Another person might choose photovoltaic systems.
If I combine measures, I pay more but might technically reach better values.
Your so-called discovery isn’t that innovative, @jx7