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"
EveundGerd4 Mar 2015 20:06I assume you have built it exactly as you described, right?
D
DerBjoern5 Mar 2015 08:52That's how we built as well. KfW70 standard with a gas condensing boiler and controlled mechanical ventilation with heat recovery. With solar thermal, we could have achieved KfW55. In our case, the solar thermal system would have cost only about €3,000 (around $3,200), as two panels would have been sufficient. However, we decided against it for aesthetic reasons.
Compensatory Measures
to Comply with the Renewable Energy Heat Act:
- The energy efficiency requirements of the current Energy Saving Ordinance are undercut by at least 15 percent
- At least half of the heat demand is covered by waste heat or combined heat and power (CHP) systems
- Heat demand is supplied directly from a local or district heating network that is largely powered by renewable energy, waste heat, CHP systems, or a combination of these energy sources.
If you can meet the compensatory measures, you are allowed to build the house with a gas boiler without solar panels…
to Comply with the Renewable Energy Heat Act:
- The energy efficiency requirements of the current Energy Saving Ordinance are undercut by at least 15 percent
- At least half of the heat demand is covered by waste heat or combined heat and power (CHP) systems
- Heat demand is supplied directly from a local or district heating network that is largely powered by renewable energy, waste heat, CHP systems, or a combination of these energy sources.
If you can meet the compensatory measures, you are allowed to build the house with a gas boiler without solar panels…
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