Energy certificates and renovation costs: what rental investors should check

Before you make an offer, check four things: what the energy certificate (Energieausweis) measures, how old the heating is and what the owners' association plans, which legal duties genuinely apply, and how much of the cost falls on you rather than your tenant. The certificate alone answers none of these, and it does not show which works are mandatory.

For a rental property investment in Germany, the energy certificate also hints at costs a home buyer does not carry: you share your tenant's carbon cost and recover only part of upgrades through the rent. For wider checks, see rental-property mistakes in Germany.

The Building Energy Act (GEG) is now the Building Modernisation Act (Gebäudemodernisierungsgesetz, GModG). It was published on 28 July 2026; its heating rules have applied since 29 July 2026, with further stages on 1 January 2027, 2028 and 2030 (BBSR GModG portal). As of 26 September 2026:

• The 65 per cent renewable rule and the age-based boiler ban are repealed. §§ 71 to 73 now read "repealed" (GModG contents; Federal Government).
• Owners choose the system, including gas, oil, heat pumps, hybrids and heat networks (§ 42 GModG).
• New gas and oil systems must blend. One installed after 29 July 2026 must draw 10 per cent of its heat from biogenic or hydrogen-based fuels from 2029, rising to 15, 30 and 60 per cent in 2030, 2035 and 2040 (§ 43(1) GModG).
• A further law is announced, not passed: the government is to present, by 1 December 2026, a law requiring suppliers to switch heating fuels fully to climate-neutral fuels from 2045 (§ 42a GModG).

Fewer mandates do not mean fewer costs: an old boiler still wears out.

It covers the building, not your flat. A certificate is issued for a building and is valid for ten years (§ 79(2) and (3) GModG). Your unit may be better or worse than the average.

There are two types. A demand certificate (Energiebedarfsausweis) calculates need from the building's construction and systems. A consumption certificate (Energieverbrauchsausweis) averages recorded use over at least 36 months (§ 82(4) GModG), so it also reflects residents' habits and vacancy.

Classes run from A+ to H, by final energy per square metre a year: A+ up to 30 kWh, D up to 130 and H above 250 (§ 86 GModG; Annex 10). The law calls certificates information for a rough comparison (§ 79(1) GModG).

You have a right to see it. When you buy an apartment, the seller or agent must show the Energieausweis at the viewing at the latest and hand it over promptly after the purchase contract (§ 80(4) GModG). Adverts must state its type, energy figure, main fuel, construction year and class (§ 87 GModG). When you let, the same duties apply to you (§ 80(5)).

Recommendations are not orders. The issuer adds modernisation recommendations (Modernisierungsempfehlungen) where cost-effective improvements are possible (§ 84(1) GModG). They are short suggestions, neither obligations nor cost estimates.

Ask what heats the building, when it was installed and who owns it. A central boiler is normally common property, so replacing it is a decision for the owners' association (Wohnungseigentümergemeinschaft, WEG). Some older flats have their own gas boiler (Gasetagenheizung); whether it is yours, and so its replacement, depends on the declaration of division (Teilungserklärung).

Useful evidence:

• Maintenance records, for installation year, fuel and repairs.
• The heating check. In buildings with at least six units, water-based systems other than heat pumps must be checked and optimised; systems installed before 1 October 2009 by 30 September 2027 (§ 60b GModG).
• The municipal heat plan. Cities above 100,000 residents had to produce one by 30 June 2026 (§ 4(2) WPG). Berlin's Senate adopted its plan on 16 June 2026 (Berlin Senate), Leipzig's council on 28 May 2026 (City of Leipzig) and Dresden's council on 24 September 2026, after publication on time (City of Dresden). A plan shows where heat networks are expected but creates no duties for owners (§ 23(4) WPG). Under the old GEG, that deadline would have brought the 65 per cent rule into force in all three cities; now it does not.

For an existing building, the standing retrofit duties are narrow:

• Top-floor ceilings below an unheated roof space that lack minimum thermal protection must be insulated, unless the roof is (§ 35(1) GModG, formerly § 47 GEG).
• Uninsulated, accessible heating and hot-water pipes in unheated rooms must be insulated (§ 69(2) GModG, formerly § 71 GEG).

The two-year deadline after a change of ownership, which many guides mention, applies only to buildings with no more than two dwellings where the owner lived on 1 February 2002 (§ 35(3); § 69(3) and (4) GModG). Buying a flat in a larger building starts no new deadline. The duties already apply to the building, and roof spaces and risers are usually common property, so outstanding work runs through the association. Ask whether it has been done.

With central heating, the largest energy costs are decided by the owners together. Read the minutes of the last three owners' meetings and the register of resolutions for heating, roof, façade and windows; the economic plan, accounts and asset report for the reserve (§ 28 WEG); and any quotes or energy advice the association holds.

If a heating replacement in the WEG has been discussed without a funding decision, assume a special levy (Sonderumlage) may follow. One resolved before you buy can still fall on you if it becomes due after you become the owner (BGH, V ZR 257/16); our checklist explains the contract clause to ask for.

Alpha Minoris's Buyer's Agent service collects these documents for purchases in Berlin, Dresden and Leipzig, including the energy certificate, WEG records, heating records and plans for works, and coordinates viewings so the heating room and roof space can be seen before you make an offer. It does not replace an energy consultant or surveyor, whose technical view remains separate and important.

With fossil heating, the carbon-price element of the heating bill is split between you and your tenant by the building's emissions per square metre (§ 5 CO2KostAufG). The landlord's share rises in ten steps from nothing below 12 kg of CO2 per square metre a year to 95 per cent at 52 kg or more (Annex). It is halved where public-law restrictions, such as a social preservation area, block major upgrades (§ 9(1)).

For a gas or oil system under the new blending duty, landlord and tenant split carbon costs and gas network charges equally from 2028, and the extra cost of the mandatory fuel share, up to 30 per cent of fuel, from 2029 (§ 5a CO2KostAufG).

An energy consultant (Energieberater) assesses performance and options and can prepare an individual renovation roadmap (individueller Sanierungsfahrplan, iSFP). Consultants for federal programmes are listed by dena (Energieeffizienz-Expertenliste). BAFA pays 50 per cent of the fee, up to €850 for buildings with three or more units, plus €250 when results are presented at an owners' meeting (BAFA). A building surveyor (Bausachverständiger) checks damp, roof, windows and pipes. Ask whether the association already holds a roadmap or survey.

No single document proves compliance or shows mandatory works. Read them together.

Budget renovation costs for a rental property from the association's documents and specialist quotes, not averages.

Grants. KfW's heating grant (programme 458) is open to condominium owners for their own unit and to WEGs for common property. A let unit receives only the 30 per cent base rate; the bonuses are for owner-occupiers. Eligible costs are capped at €28,000 for the first unit, €15,000 each for units two to six and €8,000 from the seventh, and you must apply before work starts (KfW 458). These terms apply from 21 July 2026 (Federal Government). BAFA funds individual measures such as insulation (BAFA). A grant is not cash until approved.

Rent. For a new heating system, the monthly rent may rise by no more than €0.50 per square metre within six years, after deducting public grants (§ 559(3a), § 559a and § 559e BGB). Stepped and index-linked leases restrict increases further.

Tax. Repair and modernisation costs in the first three years that exceed 15 per cent of the building's acquisition cost, excluding VAT, are depreciated, not deducted at once (§ 6(1) no. 1a EStG); see new build or existing.

Illustrative example: a WEG heating replacement

Illustrative example. Fictional building. The cost is an assumption for the arithmetic, not a price estimate.

Inputs: 12 units; your co-ownership share 80/1,000; your 60 m² flat is let. The WEG replaces the central heating at an assumed €200,000, using €40,000 from the reserve and a levy for the rest.

Plan cash on €12,800 plus a contingency; treat the grant as a possible refund. Even at the cap, the rent returns at most €360 a year.

After purchase, Alpha Minoris's Vermieter-Autopilot can coordinate works inside your unit and follow up WEG decisions in Berlin, Dresden and Leipzig; you fund the works and approve spending above agreed limits. See who handles repairs and who pays.

If you are weighing an apartment with old heating or an open WEG decision, size the levy and your reserve before you make an offer. Discuss your first rental property with Alpha Minoris.