This translation is for orientation only. Solely the German version of this page and the official KfW program sheets are legally authoritative.
We compare the EH-40 additional costs with the interest advantage of the KfW programs and the annual energy savings — factually, with three sample calculations and specified guide values.
Direct answer
Does EH 40 pay off?
In most constellations yes: The EH-40 additional costs (guide value 15.000–45.000 € depending on starting level) are often fully or largely offset by the interest advantage of the subsidy loan (in our examples around 12.000–27.000 € over ten years interest fixation, guide values Stand 2026) plus an annual energy saving of about 600–1.200 €. The higher the eligible loan amount — especially via WEF 300 with up to 270.000 € depending on program/constellation (Stand 2026, kfw.de) — the more clearly the balance is positive.
Three sample calculations in comparison
Each calculation compares the loan amount, interest assumptions, interest advantage over the interest fixation and estimated energy savings. All interest and savings values are guide values (Stand 2026) for illustration — the current daily KfW conditions are binding.
Common assumptions (guide values, Stand 2026): Interest fixation 10 years; market interest assumption 3,7 % effective p. a. (guide value, general construction financing interest level); subsidy interest assumption 2,4 % effective p. a. (guide value, programs 297/298/300). The interest advantage is the interest expense saved over the interest fixation on the subsidized loan portion (simplified, without repayment effects). Energy savings estimated compared to GEG minimum standard. Source of the program frameworks: kfw.de.
Example
Program
Loan amount
Market interest assumption
Subsidy interest assumption
Interest advantage (10 J.)
Energy savings
Balance vs. additional costs
Family with 2 childrenOwner-occupied first home, income below limit
WEF (KfW 300), EH 40
220.000 €
3,7 % (guide value)
2,4 % (guide value)
≈ 26.400 €
≈ 900 €/year
clearly positive
Couple without childrenNo WEF claim, EH 40 without QNG
KFN without QNG, EH 40
100.000 €
3,7 % (guide value)
2,4 % (guide value)
≈ 12.000 €
≈ 700 €/year
slightly to clearly positive
Family with QNGEH 40 with QNG seal, higher credit limit
KFN with QNG, EH 40 + QNG
150.000 €
3,7 % (guide value)
2,4 % (guide value)
≈ 18.000 €
≈ 900 €/year
positive, offset QNG additional costs
All values are guide values, Stand 2026, without guarantee. Interest advantage simplified as interest difference on the subsidized loan portion over the interest fixation. Binding conditions: kfw.de (Programs 297/298/300, Stand 2026).
How to read the calculation correctly
The subsidy advantage is not a payout but a saving: It arises from the difference between market interest and the lower subsidy interest, multiplied by the subsidized loan portion over the interest fixation. The larger this portion, the higher the advantage — therefore the family with WEF loan falls most clearly positive in our first example. Which programs you can combine and how high the credit limit is per constellation is shown in our overview of the subsidy programs.
The second component is the EH-40 additional costs. They depend heavily on the starting level: If a high efficiency standard is already series at the provider, the surcharge remains small. We calculate on the page what the additional costs are composed of in detail — building envelope, windows, heat pump, ventilation, PV, planning and verification Additional costs EH 40 in detail. Whether the additional QNG seal is worth it is explained on the page QNG additional costs.
Important for the comparison with the renovation subsidy: This calculation concerns exclusively the new construction. Subsidies for the energy renovation of existing buildings or the BAFA heating subsidy for existing buildings follow other rules and are not covered here. First check the technical requirements and the application process, before you finalize the numbers.
Frequently asked questions: Is KfW 40 worth it?
Answers on the cost-effectiveness of the efficiency house 40 standard — with reference to the underlying guide values.
From when does the KfW-40 standard pay off financially?+
The calculation depends on three factors: the EH-40 additional costs compared to the GEG standard (guide value 15.000–45.000 € depending on starting level and house type), the interest advantage of the subsidy loan and the annual energy savings. In our three sample calculations the interest advantage over a ten-year interest fixation is around 13.000–27.000 € (assumption market interest 3,7 % vs. subsidy interest 2,4 %, guide values Stand 2026); together with an energy saving of about 600–1.200 € per year, the subsidy advantage covers the additional costs in many constellations fully or to a large extent. All figures are guide values — the current daily conditions according to kfw.de are binding.
Are the mentioned interest rates binding?+
No. The subsidy interest used in our examples (assumption 2,4 % effective, guide value Stand 2026) and the market interest (assumption 3,7 % effective, guide value Stand 2026, source: general interest level for construction financing) serve exclusively for illustration. KfW publishes the actual current daily conditions for programs 297/298 and 300 on kfw.de; they may vary depending on interest fixation and term. Always use the current values for your decision.
How strongly does EH 40 reduce ongoing energy costs?+
An efficiency house 40 significantly falls below the permissible annual primary energy demand of the GEG reference building. In practice, this means a saving of about 600–1.200 € per year for a typical new build with heat pump compared to the GEG minimum standard (guide value, depending on living area, user behavior and electricity price). Over 20 years this adds up to a five-digit amount — even more if energy prices rise.
Is the additional QNG seal worth it for KFN?+
The QNG seal increases the maximum loan amount for KFN (297/298) from 100.000 € to 150.000 € per residential unit; for WEF with QNG the framework also rises (Stand 2026, kfw.de). This larger low-interest loan is offset by QNG additional costs for certification, sustainability consulting and if applicable ecological balancing. Whether it pays off depends on the ratio of the QNG additional costs to the additional interest advantage of the higher loan — we calculate the details on our QNG additional costs page.
What happens if the interest rates fall again?+
The subsidy advantage arises from the difference between the market and subsidy interest rate. If the general interest rate level falls, the difference shrinks — the KfW advantage becomes smaller. Conversely, a rising market interest rate level increases the advantage. Because both interest rates are fixed at the time of commitment, the current difference at that time always applies to your financing. Our examples use a snapshot (reference values Stand 2026) and must be updated accordingly.
Is the Efficiency House 40 standard already included in the price for prefabricated houses?+
For many providers, a high efficiency standard is already part of the standard equipment, so that the EH-40 additional costs are lower than in new buildings with simple basic equipment. The decisive factor is the specific offer: Have the permissible annual primary energy demand and the proven efficiency house standard confirmed in writing before calculating the additional costs.
Calculate your specific situation
The subsidy finder matches your situation to the appropriate programs — as a starting point for the individual cost-effectiveness calculation with daily updated conditions.
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