The German Federal Ministry for Economic Affairs and Energy (BMWi) promotes measures to increase energy efficiency.
You can receive funding for the following measures:

• large solar collector systems with more than 40 square meters of gross collector area,
• large solid biomass combustion plants,
• heating networks fed by renewable energy sources,
• biogas pipelines for non-processed biogas,
• large heat storage tanks,
• large efficient heat pumps,
• Plants for combined electricity and heat production (CHP).

No subsidies are granted

• for self-built plants and used plants,
• for prototypes (plants of which there are less than 4 copies),
• if you are a manufacturer of eligible plants or their main components,
• for trust constructions,
• for so-called in-itself transactions, such as acquisition from the property of a spouse,
• for debt rescheduling and follow-up financing of measures that have already been started,
• if you have already started the measure before submitting the application.

The federal government, the states and their institutions are also not subsidized.

If you want to use heat from renewable energy sources, then you can get a loan of up to EUR 25 million.
The amount of the subsidy for the repayment of the loan depends on the type, use and performance of your system:

• Solar collector systems:
  • You get up to 30 percent of the eligible costs as a subsidy if you use your solar collector system for hot water production, space heating, solar cooling and feeding into a heating network.
  • You receive up to 40 percent of the eligible costs as a grant if you feed the majority of produced heat into a heating network with at least four consumers.
  • If your solar collector system is subsidized based on yield, your subsidy is calculated as follows: annual heat yield * number of solar thermal modules * EUR 0.45.
    
• Biomass plants for the combustion of solid biomass for thermal use:
  • You receive a basic subsidy of up to EUR 20 per kilowatt (kW) of installed nominal heat output. You can receive a maximum subsidy of EUR 50,000.
  • You can also receive a bonus of up to EUR 20 per kW of installed nominal heat output if your system has low dust emissions or if a buffer tank is installed.

With the basic subsidy and bonus payments together, you can receive a maximum subsidy of EUR 100,000.

• Combined heat and power biomass plants:
  • You will receive EUR 40 per kW of installed nominal heat output as a grant.
    
• Heat grids fed predominantly from renewable energy sources:
  • You get EUR 60 for each newly built meter of the heat network, but maximum EUR 1 million subsidy.
  • If you feed in heat from deep geothermal plants, you can receive up to EUR 1.5 million in subsidies.
    
• large heat storage facilities:
  • You get EUR 250 for each cubic meter of storage volume. The subsidy is limited to 30 percent of investment costs. You can receive a maximum of EUR 1 million in subsidies.
    
• Biogas pipelines for unprocessed biogas:
  • You get up to 30 percent of the eligible costs as a grant.
    
• large efficient heat pumps:
  • For heat pumps, you receive EUR 80 per kilowatt of heat output as a subsidy.
  • For a geothermal probe, you will receive EUR 4.00 for each meter up to a depth of 400 meters and EUR 6.00 for depths of 400 meters or more as a subsidy.

If you

• a company
  • with less than 250 employees
    and
  • have less than EUR 50 million in annual sales
    and
  • the heat and/or energy produced by your plant is used for the operation of a small or medium-sized enterprise (SME),

then your total grant will increase by 10 percent.

Small and medium-sized enterprises have

• less than 250 employees
  and
• An annual turnover of no more than EUR 50 million.

Eligible costs are:

• only investments in the plant itself (primary heating circuit),
• technical and commercial planning costs.

Not eligible are:

• Piping, distribution or control in the secondary heating circuit,
• radiators, air heaters and other space heaters.

You will not receive the repayment subsidy until you have completed your measure. To do this, you must prove

• that you have spent the money from the loan on the measure,
• that the measure technically fulfills its purpose.

You must keep all invoices and receipts related to eligible costs.

Applications for funding are processed by the Kreditanstalt für Wiederaufbau (KfW).

You are not entitled to the approval of the subsidy.

Note
Through the "Renewable Energies - Premium" promotional program, small companies with fewer than 50 employees and annual sales of no more than EUR 10 million can also apply for a loan with a repayment subsidy (KfW promotional loan for renewable energies (Premium) - No. 271/281 approval for small companies (281)).