GEG 2024/2026 for a Prefab House: the Obligations and Their Costs
The Building Energy Act (GEG) sets which energy standard your prefab house must reach in 2026 – and therefore a noticeable part of the price. We explain the efficiency house levels, the 65% renewables rule, the permitted heating systems and the extra costs each requirement brings for the building application, contract and KfW funding.
Anyone who wants to calculate house prices realistically in 2026 cannot get past the Buildings Energy Act (Gebäudeenergiegesetz, GEG): it determines the energy standard that every new prefabricated house must reach and thus causes a considerable part of the construction costs. The required share of renewable energy, the permissible heating technology and the insulation levels have a direct effect on the price per square metre. This guide classifies the efficiency house (Effizienzhaus) levels, the 65 percent rule and the resulting additional or reduced costs for the building application, construction contract and KfW funding – with prices as of May 2026. An overall overview is provided by our guide to the prefabricated house at a glance; the effects on your project can be worked out in the prefabricated house cost calculation.
What the GEG 2026 prescribes – and what it costs you
Short answer: The Buildings Energy Act has combined the requirements from the EnEV, EnEG and EEWärmeG into one set of rules since 2020. In 2026 it applies to every new build, every major renovation and every heating replacement – for a prefabricated house just as for a masonry house. In terms of price, above all four levers carry weight: primary energy demand, heat transmission values, the RE share of the heating and the mandatory energy performance certificate. The government-mandated requirement of 65 percent renewable energy for every new heating system is the biggest cost driver of the building services. Your house is assessed against the virtual reference building. Anyone who calculates GEG-compliant from the start can partly offset the additional costs via the federal programme Climate-Friendly New Construction of the BMWSB.
What sounds dry on paper means effort and costs in practice: every building application requires an energy performance certificate under the GEG and an RE proof in 2026. These calculations are prepared by an energy efficiency expert from the BAFA list – with the companies we compare, this item is already contained in the stated house prices and does not have to be paid separately. Without a GEG-compliant calculation, the building authority grants no permit. How this affects the process and the additional costs is shown by the building permit guide.
Efficiency house levels 2026: the costs of EH 55, EH 40, EH 40 NH and QNG
Short answer: The efficiency house level indicates how much energy a house consumes in relation to the statutory reference building – and the lower the number, the higher the construction costs turn out. EH 55 stands for 55 percent of the reference demand, EH 40 for only 40 percent, and EH 40 NH combines this with the sustainability seal QNG. For the KfW funding, EH 55 forms the lower limit in 2026; the low-interest programmes KFN 297/298 require EH 40 or QNG respectively – in return, the financing price sinks on balance.
Efficiency house levels 2026 including funding framework in a price comparison
| Level | Primary energy demand | Transmission loss | KfW funding 2026 |
|---|---|---|---|
| EH 55 | 55 % of reference | 70 % of reference | Yes, KFN level not applicable |
| EH 40 | 40 % of reference | 55 % of reference | KFN 297, up to €100,000 |
| EH 40 NH (with QNG) | 40 % + sustainability | 55 % of reference | KFN 298, up to €150,000 |
| EH 40 Plus (PV+storage) | 40 % + self-consumption | 55 % of reference | phasing out, regional |
Of the 140 compared providers, around 95 percent already offer the EH 55 standard as standard in 2026 – it is fully included in the base price. The jump to EH 40 costs an additional 8,000 to 25,000 euros. EH 40 NH with the Sustainable Building quality seal requires further proofs on life cycle, freedom from pollutants and recyclability – here the surcharge ranges between 12,000 and 35,000 euros, which, however, is offset by a higher KfW subsidy. How these amounts add up is shown by the KfW funding guide 2026.
The 65 percent rule: which heating fits the budget in 2026
Short answer: For every heating system newly installed in a new build from 2024, the rule is: at least 65 percent of the heat must come from renewable sources. Permitted in 2026 are the heat pump (air, brine, water), the hybrid solution of heat pump and gas for peak loads, direct electric heating in efficiency houses, solar thermal with wood or pellets as well as the connection to a district heating network with at least a 65 percent RE share. Pure gas or oil heating systems are practically ruled out in new builds. In terms of price, these options differ clearly – from the cheap air heat pump to the expensive brine system.
- Air-to-water heat pump (in 2026 the cheapest standard solution in the prefabricated house, COP 3.0–4.5).
- Brine-to-water heat pump with ground collector or geothermal probe (more efficient, but at €18,000–32,000 the most expensive heat pump variant).
- Hybrid heat pump with gas peak load (loses appeal because gas costs rise in the medium term).
- Pellet heating plus solar thermal (something for timber-house fans, more maintenance-intensive and more expensive in operation than a heat pump).
- District heating from renewable sources (in conurbations often the cheapest solution; check for a connection obligation in the development plan).
- Hydrogen-ready heating (legally permissible, but in 2026 neither market-ready nor attractively priced).
Seasonal performance factor (JAZ), COP values, buffer storage and the running costs of the heat pump are explained by the heat pump guide. How operating costs can be pushed down with solar power is shown by our PV guide. For the low flow temperatures of a heat pump, the underfloor heating in new builds is the ideal heat distribution system. Which technology fits best on balance is clarified by our comparison of heating systems in new builds.
U-values 2026: which insulation values are already included in the price
Short answer: Annex 1 of the GEG determines the heat transmission coefficients of the reference building. For a typical single-family house, the following apply as a reference in 2026: external wall ≤ 0.28 W/(m²·K), roof ≤ 0.20 W/(m²·K), floor slab to the ground ≤ 0.35 W/(m²·K), windows ≤ 1.3 W/(m²·K) and external door ≤ 1.8 W/(m²·K). The good news for the calculation: prefabricated houses are as standard clearly below these values in 2026 – external walls at 0.15–0.18 W/(m²·K), roofs at 0.12–0.15 W/(m²·K), without a surcharge being incurred for this.
U-values 2026 — the GEG reference compared with the included standard series specification
| Component | GEG reference | Provider standard | EH 40 / Premium |
|---|---|---|---|
| External wall | ≤ 0.28 | 0.17 | 0.12–0.15 |
| Roof against outside air | ≤ 0.20 | 0.14 | 0.11–0.13 |
| Floor slab to the ground | ≤ 0.35 | 0.22 | 0.16–0.19 |
| Windows (Uw) | ≤ 1.3 | 1.1 | 0.75–0.90 |
| External door | ≤ 1.8 | 1.4 | 0.90–1.10 |
| Thermal bridge surcharge ΔUWB | 0.05 | 0.03 | 0.01–0.02 |
That the series values are so far below the reference relieves your budget and has two reasons: firstly, timber frame construction insulates very economically even with slim wall thicknesses (usually 30–36 cm), because a lot of insulating material meets little structure. Secondly, the required EH 55 standard demands good envelope components in the overall balance anyway, since ventilation losses and building services would otherwise drive the primary energy demand over the limit – exceeding the requirement is therefore already factored into the base price.
A GEG-compliant prefabricated house at a calculable fixed price
All 140 companies in the comparison offer the EH 55 level as standard at a fixed price in 2026. We disclose the surcharges for EH 40 and QNG transparently – so you know precisely in advance which house prices you can expect.
Controlled residential ventilation (KWL): a cost item or a saving?
Short answer: A controlled residential ventilation with heat recovery (KWL-WRG) is not legally prescribed in any federal state in 2026, but in EH 40 houses it is practically without alternative, because the energy balance does not otherwise add up. Although the GEG allows window ventilation, it calculates with a 0.5 1/h air change for the ventilation loss – a value that airtight envelopes cannot hold over the year without KWL. As a cost item, the system comes to 7,500 to 14,000 euros including distribution ducts in 2026, but in return saves running heating costs.
A modern KWL recovers 85 to 92 percent of the heat – the exhaust air preheats the incoming fresh air in the counterflow principle. In well-insulated houses the ventilation loss thus falls by up to 75 percent, which is directly reflected in lower operating costs. In addition, filters (F7/F9) raise the air quality and relieve allergy sufferers. Set against this are running costs: the maintenance effort (filter change twice a year), the power consumption of the fans (40–80 W continuous load) and possible noise with poorly dimensioned systems. Which systems are suitable for planning a ventilation system in new builds is compared by the separate guide.
GEG in the building application: which proofs drive up the additional costs
Short answer: Three GEG proofs must be included in the building application in 2026 and make up part of the additional building costs: first, the energy demand certificate under the GEG with the primary energy, final energy and transmission heat loss of the specific house; second, the proof of the mandatory RE share including a detail sheet on the heating; and third, the summer heat protection proof under DIN 4108-2. With KfW funding, further documents are added (KfW application form, financing confirmation from the house bank, if applicable QNG proof) – with many providers these services are already included in the price.
- Energy demand certificate under the GEG (prepared by an energy efficiency expert from the BAFA list, often included in the house price).
- Detailed calculation of the RE share of the heating (heat pump, solar thermal, wood, district heating).
- Summer heat protection proof under DIN 4108-2 (overtemperature degree hours).
- Documented hydraulic balancing of the heating.
- Ventilation concept (also with window ventilation, as proof against mould risk).
- For the KfW application: trade-by-trade proofs on component U-values, building services and renewable heat.
An expensive mistake with the energy performance certificate
Only a certified energy efficiency expert from the BAFA list may issue the energy performance certificate. It becomes tricky if a provider prepares the certificate internally but does not officially register it – at the latest with the KfW application this becomes apparent and can jeopardise the building application as well as the funding and thus your entire financing. Before signing, request the written BAFA-list entry of the responsible expert.
GEG in existing buildings: when costs threaten during a renovation
Short answer: With an existing house, the GEG applies in three cost-relevant cases in 2026: first, with a heating replacement – the 65 percent RE obligation applies to new systems from 2026 in new development areas, from 2028 in large cities with at least 100,000 inhabitants and from 2028 in smaller municipalities, with a transition period until mid-2029; second, with a comprehensive envelope renovation (from 10 % of the component area), where the U-values from Annex 7 must be met; third, with an extension – from an annex of 50 m², the GEG applies fully to the annex and makes it correspondingly more expensive.
Anyone modernising an older prefabricated house from the 1970s to 1990s should therefore calculate precisely in advance which components they touch and which GEG costs they trigger with this. Renovation packages including funding and price framework can be found in the modernisation guide. A look at the BEG (Federal Funding for Efficient Buildings), which forms the funding landscape parallel to the GEG, additionally pushes down the modernisation costs.
Beyond the GEG, further requirements and technology decisions apply in new builds: which states prescribe a PV system is shown by the guide solar obligation for new builds, and which heat pump suits your plot is clarified by the comparison air or ground-source heat pump?
Outlook: how the GEG will shape prices up to 2030
Short answer: By 2030, two tightenings are emerging that will feed through to house prices: first, the raising of the new-build minimum standard from EH 55 to EH 40 (planned for 2027/2028; the EU directive EPBD requires "zero-emission buildings" in new construction from 2030) and second, the nationwide extension of the RE obligation in existing buildings from mid-2029. Anyone who builds a KfW 40 house in 2026 pays more today but saves later retrofitting; anyone who relies on EH 55 builds more cheaply and quickly but has to add on with a later extension.
Market observation 2026: more and more providers are elevating EH 40 to the standard, while EH 55 becomes the economy variant. Premium houses from Baufritz, Schwörer and FingerHaus already deliver EH 40 NH (QNG) for a surcharge of €12,000–25,000. Anyone who plans long-term and uses the KFN 298 often fares more cheaply on balance with EH 40 NH in 2026 than with EH 55, thanks to the better funding conditions.
GEG-compliant and KfW-funded – so the price stays calculable
Three companies from our 40-manufacturer comparison will work out fixed-price quotes at EH 40 level including the KfW application for you. We bundle your enquiry and disclose the additional costs transparently.
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Compare house prices nowImportant questions briefly explained
The most common price questions around GEG 2024/2026 for a Prefab House – answered concisely by the Prefabricated House editorial team (as of 2026).
