Advantages of KFW 40 Plus in General

Hello everyone,

even though the topic of the "right" building technology and the different advantages has been widely discussed, I still cannot answer the general question of the profitability of a Kfw 40 plus house for myself.

In many places in the forum, you read that for purely economic reasons the pure Energy Saving Ordinance standard is recommended and that the additional costs for a KFW house usually do not amortize. I find that hard to understand.

We are currently planning the new construction of a single-family house in solid construction, without a basement, with about 200m^2 of living space and underfloor heating. Without going too much into depth now (even though general and undetailed comparisons are always difficult) I would like to set up the following greatly simplified calculation:

Additional costs for KFW 40 plus compared to Energy Saving Ordinance standard:
Ground source heat pump (deep drilling): €12,000 (€20,000 instead of gas boiler with solar for €8,000)
Controlled residential ventilation with heat recovery: €12,000
Photovoltaic system with storage: €15,000
Total additional costs: €39,000

Subsidy:
Repayment waiver through KWF 40 plus: €15,000
BAFA subsidy for geothermal energy: €4,500

Remaining additional costs: €19,500

Is it actually the case that these additional costs of €19,500 do not amortize over a reasonable period? (There are indeed further costs for KWF 40 plus, e.g. for construction supervision, but these are mostly also subsidized, for example through the program KFW 431).
In addition, you receive the low-interest loan (currently 0.9%) up to €100,000 from KFW and other banks do not treat KFW loans as loans and thus grant higher creditworthiness.

Would you still say that a KFW 40 plus house is not economically worthwhile based on these values?

Thank you very much for your assessments!

19500 additional costs. The house with gas would have around 1000,- gas costs per year and 2000 kWh electricity per year for two people, correspondingly more for three, etc. The kfw 40 plus house saves the gas, 19.5 years until break-even, but due to the geothermal heat pump and controlled residential ventilation, the electricity demand will certainly double. So you are clearly in the area of 30 years until break-even. If you also calculate against it, if you had not invested your 19500,- in kfw 40 but instead for 30 years in ETFs on the Dax or SP, then it becomes completely unprofitable. K.

So I have an Energy Saving Ordinance standard house from 2016 and pay a monthly installment to the energy supplier of €47 (heating and hot water). Now you can also calculate with €50 and pretend as if your house consumes no energy at all.

P.S. Remember that the higher system investment costs interest until the end of the useful life. Feel free to add opportunity costs as well. The claim that the KFW loan provides better conditions is also a myth. More technology also means higher maintenance costs (batteries, inverters, filter changes, ...) – hard to quantify, more for some and less for others, but the first two examples should be replaced once within your "payback period," so now do the math.

One could also see it differently in my opinion:

Controlled residential ventilation with heat recovery is, in my view, very useful; I wouldn't want to do without it anymore. You have to decide whether you want it or not. There are many discussions about it. A controlled residential ventilation system will never pay for itself; it has to be considered a luxury.

Photovoltaic systems without storage are profitable in most cases and have probably amortized after about 10 years. And if you are already in the KfW40 range, you might as well go for KfW40+, then the storage is included due to the higher subsidy.

Whether deep drilling is worthwhile for a KfW40 house has to be questioned. You could certainly also opt for surface, ring trench collectors, etc., depending on whether you want or can do something yourself. Or you go straight for an air-water heat pump, but then the BAFA subsidy might be tight.

Thank you very much for your answers!

What World-e is addressing are exactly the thoughts currently on my mind. In general terms, it’s just one more system to move into the next subsidy class. And especially if you believe that controlled residential ventilation is indispensable in a new building (which seems to be the consensus in the forum, even though I previously thought otherwise), the path to KfW 40 is not far, and geothermal energy comes almost "for free" through the subsidy (to put it simply).

One could certainly also go for surface collectors, trench collectors, etc., depending on whether you can/want to do something yourself. Or you could go straight for an air-to-water heat pump, but then the BAFA subsidy might be tight

My architect is quite convinced by the deep drilling, and all his clients are highly satisfied with it (he is a relative, so there is full trust). But of course, this is a widely discussed topic anyway. Due to numerous other considerations, we would therefore decide on deep drilling if we go for a heat pump.

The KfW 40 plus house saves gas, 19.5 years to break-even, but due to the geothermal heat pump and controlled residential ventilation, electricity demand will probably double. So in the end, you are clearly in the area of 30 years to break-even.

However, with the combination of a photovoltaic system, you would probably have a high degree of self-consumption of the produced electricity. Do you think this advantage is offset by the increased electricity demand from the heat pump and controlled residential ventilation? I had so far thought that with a suitably sized photovoltaic system and as much self-consumption as possible, electricity costs can be reduced overall (despite increased electricity demand). And therefore, a payback period of significantly less than 30 years can be achieved.

Remember that the higher system investment incurs interest costs, and that until the end of the lifetime. Also consider opportunity costs.

These are of course important points. The additional interest at 0.9% on €19,500 is manageable, however. Regarding opportunity costs, you are absolutely right.

even though the topic of the "right" system technology and the different advantages has already been discussed many times, I still cannot answer the general question of the advantage of a KFW 40 plus house for me.

An exciting question that I have also been thinking about for a while.
However, it is hard to find concrete information.

Additional costs for KFW 40 plus compared to Energy Saving Ordinance standard:
Brine heat pump (deep drilling): €12,000 (€20,000 instead of gas boiler with solar for €8,000)
Controlled residential ventilation with heat recovery: €12,000
Photovoltaic system with storage: €15,000
Total additional costs: €39,000

Funding:
Repayment waiver through KWF 40 plus: €15,000
BAFA funding for geothermal energy: €4,500

Remaining additional costs: €19,500

I think you still forgot decisive points here, such as higher planning effort and the building envelope with insulation, windows, etc.
I would calculate those at at least €20,000 again for such a large house (200 m²).

For me, the same amount comes out according to this calculation:
Because I want controlled residential ventilation anyway because of comfort, it is therefore irrelevant in the comparison.
Photovoltaics also pay off by themselves, so they also do not need to be included in the comparison.
I actually do not want gas in the house either, but it is hard to just leave that out.
Then the remaining additional costs are: planning, envelope, storage, heating system with €30,000.
If everything goes well, you might break even after 30 years.

For smaller houses it could also be cheaper, or with a granny flat.