The heat plan is out: what owners with gas heating must decide now – and what not

The short answer

A municipal heat plan obliges owners to nothing: it has no legal effect on third parties, and since the Gebäudemodernisierungsgesetz (GModG, Building Modernisation Act) no heating obligation is tied to it any more. But it answers the question that comes first with every heating replacement: will a heat network come here, or is the building on its own?

So anyone with a working gas boiler does not have to decide anything today. Anyone who will have to replace it in the next few years should read their municipality’s heat plan first.

When does the heat plan have to be in place?

The Wärmeplanungsgesetz (WPG, Heat Planning Act) obliges the federal states to ensure a heat plan for every municipal area (§ 4 WPG). The deadlines depend on the population on 1 January 2024:

Municipality size	Deadline for the heat plan
more than 100,000 inhabitants	30 June 2026
100,000 inhabitants or fewer	30 June 2028
fewer than 10,000 inhabitants	30 June 2028, states may provide a simplified procedure

Source: § 4(2) and (3) WPG.

Plans already drawn up under state law remain valid (§ 5 WPG). The plan is adopted by the municipal council or the competent body and published online (§ 23(3)). In addition, the Federal Ministry for Economic Affairs is to make all plans available centrally, for the first time six months after the relevant deadline (§ 34), so for the large cities from the end of December 2026. The plan is reviewed every five years and updated where necessary (§ 25).

What does the plan say about my property?

The municipality divides its area into expected heat supply areas for the reference years 2030, 2035 and 2040 (§ 18(3) WPG). There are four types: heat network area, hydrogen network area, area for decentralised heat supply and review area, where the situation is still open (§ 3 WPG). For each area the municipality assigns one of four suitability levels, from “very likely suitable” to “very likely unsuitable” (§ 19(2)).

The word “expected” is meant seriously. The classification creates no obligation to use or provide a particular type of supply, and no right to be placed in a particular area (§ 18(2)). A heat network area in the plan therefore does not mean that a network operator has to build the connection. And a hydrogen network area does not mean that hydrogen will arrive at a particular price.

Does the plan turn into an obligation?

Three levels need to be distinguished:

Level	Legal basis	Obligation for the owner?
Heat plan adopted	§ 23(4) WPG	no, no external effect
Designation as a heat network or hydrogen network expansion area	§§ 26, 27 WPG	no, no obligation to use; only relevant to land-use planning and official discretion
Mandatory connection and use by municipal bylaw	state law, § 109 GModG	yes, but only if the municipality adopts it

Until July 2026 things were different. Under the old Gebäudeenergiegesetz (GEG, Buildings Energy Act), the transition periods of the 65 per cent rule were linked to heat planning. With the GModG, §§ 71 to 71p were dropped; the term heat plan no longer appears in today’s legal text. When replacing a heating system, § 42 GModG offers ten equivalent options, from a heat pump to a substation connecting to a heat network to a new gas boiler.

What does a new gas boiler cost after the heat plan? A worked example

Equivalent does not mean equally expensive. Anyone who installs a new gas or oil heating system in an existing building after 29 July 2026 must, from 2029, generate a rising share of the heat from biomethane, bio-oil or hydrogen (§ 43 GModG). Under contracting, the operator meets this obligation, not the owner (§ 43(6)). For rented flats there is also the cost split under § 5a CO2KostAufG: from 2028, landlord and tenant each bear half of the CO₂ costs and the gas network charges, and from 2029 also the extra costs of the bio share up to 30 per cent.

Assumptions: 12 flats, new gas boiler in 2027, consumption of 180,000 kWh a year as in the CO₂ price example. Nobody knows today how much more biomethane will cost than natural gas in 2029 or 2040. The table therefore uses a unit of calculation: per 1 cent surcharge per kilowatt hour.

From	Required share	Biogenic quantity	Extra cost per 1 ct surcharge	of which landlord (§ 5a)
2029	10 %	18,000 kWh	€180	€90
2030	15 %	27,000 kWh	€270	€135
2035	30 %	54,000 kWh	€540	€270
2040	60 %	108,000 kWh	€1,080	€270

At a 5 cent surcharge, that would be around €5,400 of extra cost a year in 2040, €1,350 of it borne by the landlord. On top comes the 50:50 CO₂ split for the fossil remainder: using the emission factor in EBeV 2030 (around 0.181 kg CO₂ per billed kWh of natural gas), the building emits around 33 tonnes today. From 2028 the price for this is, as things stand, to be set in the European emissions trading system; its level is open.

This is exactly where the heat plan becomes valuable. If the building lies in an area where the municipality rates a heat network as very likely suitable by 2030, the gas boiler competes with a connection whose pricing rules should be checked beforehand, as the CJEU ruling on district heating price clauses shows. If it lies in an area for decentralised supply, no network is to be expected, and the calculation is between heat pump, hybrid and gas with the bio-fuel ladder. What a kilowatt hour costs today for each option is in the full cost comparison.

What about the hydrogen network area?

A hydrogen network area in the plan is a planning assumption, not a promise of supply. Anyone who buys a gas boiler today on the argument that hydrogen will come later still needs the bio-fuel ladder from 2029, and bears the fuel costs themselves. In addition, a law introducing a green gas/green heating oil quota is to be presented by 1 December 2026, obliging suppliers to make fuels for building heat fully climate-neutral by 2045 (§ 42a GModG). What this means for prices remains open as long as there is no draft.

What owners should do now

1. Find your municipality’s heat plan. Large cities had to draw it up by 30 June 2026; it is published on the municipality’s website.
2. Classify your own property: note the area type for 2030, 2035 and 2040 and the suitability level.
3. Check whether the municipality has also formally designated an area or adopted mandatory connection and use. Only mandatory connection creates an obligation.
4. Keep a working heating system running. Neither the plan nor the GModG requires early replacement.
5. Plan ahead for a breakdown: obtain quotes for at least two options while there is no time pressure.
6. For a new gas or oil boiler, factor the bio-fuel ladder and the 50:50 cost split under § 5a CO2KostAufG into the calculation with several surcharge scenarios.
7. If the plan provides for a heat network, ask the network operator about the timetable, connection costs and price adjustment clause before ordering a new boiler.