Hello everyone,
we are currently planning our house and are considering whether the extra cost from KfW55 to KfW40 plus is "worth it." By worth it, I mean both the payback period and, of course, other advantages and disadvantages, such as a central ventilation system versus a decentralized one.
Our general contractor offers the following standard options (alternatives are possible in consultation):
My specific questions are:
1) What potential savings can be expected due to lower heating costs, electricity costs, and feed-in tariffs, assuming energy price increases, maintenance, repairs, or total failure of components are excluded? I understand that many factors play a role and this is hard to calculate, but perhaps it is possible to give at least a rough range based on comparison values and considering the following information:
2) What other advantages and disadvantages exist between KfW40 plus and KfW55?
3) Any further tips on how to make a good decision?
Thank you very much in advance for your assessment!
J.
we are currently planning our house and are considering whether the extra cost from KfW55 to KfW40 plus is "worth it." By worth it, I mean both the payback period and, of course, other advantages and disadvantages, such as a central ventilation system versus a decentralized one.
Our general contractor offers the following standard options (alternatives are possible in consultation):
- KfW 55 (no extra cost): aerated concrete blocks 36.5 cm (14 inches), air-to-water heat pump, underfloor heating, decentralized ventilation system
- KfW 40 plus (€25,000 surcharge): aerated concrete blocks 42.5 cm (17 inches), air-to-water heat pump, underfloor heating, central ventilation system, photovoltaic system + energy storage
My specific questions are:
1) What potential savings can be expected due to lower heating costs, electricity costs, and feed-in tariffs, assuming energy price increases, maintenance, repairs, or total failure of components are excluded? I understand that many factors play a role and this is hard to calculate, but perhaps it is possible to give at least a rough range based on comparison values and considering the following information:
- The house is located in NRW (mild climate)
- Roof orientation and pitch are almost ideal for photovoltaic
- The house has no basement and with the 42.5 cm (17 inches) blocks a living area of 190 m² (2045 sq ft)
- 2 adults and 2 small children
- 3 kWp photovoltaic system, 6.5 kWh battery (assumed)
- Indoor temperature about 23°C (73°F), bedrooms about 21°C (70°F)
- I am aware of the additional KfW funding options; however, the interest rate of the KfW loan is less favorable than that of our bank, so the advantage would be reduced to €8,150
2) What other advantages and disadvantages exist between KfW40 plus and KfW55?
3) Any further tips on how to make a good decision?
Thank you very much in advance for your assessment!
J.
Lumpi_LE schrieb:
No, with KfW it’s only 50 or 60 now, which is noticeably different compared to 70.Do you have a source for that? I’ve never heard of it. I have KfW40 without the plus, so only photovoltaic without storage. For me, it’s normally set to 70% soft.On sunny days, depending on the system size, 40-60 kW come from the roof. You can neither use nor store this energy efficiently. Therefore, subsidies for energy storage should always be considered critically. Maybe 60% efficiency is still acceptable, but at 50%, it stops making sense.
Specki schrieb:
With good battery management, this shouldn’t be an issue. The battery should be prioritized for charging once it exceeds 60%. As @guckuck2 already mentioned, this is completely irrelevant.
We also had a battery subsidy program. It would have been 3000€ for a 10 kWh battery, but limited to, I believe, 60% state of charge (the supply temperature limit was also 50°C (122°F)). I then calculated the losses using a somewhat more complex Excel spreadsheet, and the result was almost exactly 3000€.