How Much Does an Energy Retrofit Cost?
An energy retrofit is one of the largest investments a homeowner can make, but it pays off through lower energy costs and government subsidies in the long run. Total costs depend on the chosen measures and can range from 10,000 euros for individual measures to over 100,000 euros for a complete retrofit.
Costs of Individual Measures
Facade Insulation: 15,000 to 40,000 Euros
Facade insulation is one of the most effective measures for energy savings. For a typical single-family home (120 square meters of living space, approximately 150 square meters of facade area), an external thermal insulation composite system (ETICS) with 16 cm insulation thickness costs between 150 and 250 euros per square meter. The annual heating energy savings amount to 15 to 30 percent. The KfW subsidizes this measure at 15 percent of costs (plus 5 percent iSFP bonus).
Roof Insulation: 10,000 to 25,000 Euros
Roof insulation can be carried out as above-rafter insulation (80 to 200 euros per square meter), between-rafter insulation (40 to 80 euros per square meter), or blown-in insulation (15 to 40 euros per square meter). Energy savings amount to 10 to 25 percent of heating energy.
Window Replacement: 8,000 to 20,000 Euros
Replacing old windows with modern triple glazing costs 500 to 1,500 euros per window (depending on size and material). A single-family home with 10 to 15 windows comes to 8,000 to 20,000 euros. Energy savings amount to 10 to 20 percent.
Heating System Replacement: 15,000 to 35,000 Euros
Switching to a heat pump costs 15,000 to 25,000 euros (air-to-water) or 20,000 to 35,000 euros (ground-source with borehole) depending on the type. A pellet heating system costs 18,000 to 28,000 euros. The KfW subsidizes heat pumps at 30 percent of costs and pellet heating at 20 percent.
KfW Subsidies Overview
The Federal Funding for Efficient Buildings (BEG) offers the following subsidy rates: heat pumps 30 percent, biomass (pellet) 20 percent, solar thermal 25 percent, building insulation 15 percent, windows and doors 15 percent, and ventilation systems with heat recovery 15 percent. The iSFP bonus of 5 percent is added when an energy consultant has prepared an individual renovation roadmap. The maximum eligible amount is 60,000 euros per measure per housing unit.
Requirements Under the Building Energy Act (GEG)
The GEG mandates various renovation requirements: upon change of ownership, the top-floor ceiling must be insulated and heating boilers over 30 years old must be replaced. From 2024, the 65-percent renewable energy requirement applies to new heating systems. Exceptions apply to homes that have been owner-occupied since at least February 1, 2002.
Return on Investment: When Does the Investment Pay Off?
The payback period depends on energy prices and subsidy amounts. Example calculation for facade insulation: investment of 30,000 euros minus 6,000 euros KfW grant equals a net outlay of 24,000 euros. Annual heating cost savings of 2,000 euros means payback after 12 years. With rising energy prices, the payback period shortens. Additionally, the property value increases due to better energy efficiency.
Our renovation cost calculator estimates the expected KfW subsidy for each energy measure and shows the net cost after funding. This gives you a quick decision-making basis for your renovation planning.