You can read all of this in the corresponding brochure: information sheet "BEG Residential Buildings - Grant" in version 10/21. I must also clarify the matter again: you have to submit invoices for everything that is funded (see "Information sheet on eligible measures"), but beware: "Own work and the material costs incurred are not eligible for funding. Only services from specialized companies and the costs of materials installed by an external specialized company are recognized. Private execution, even by craftsmen, is not eligible. A commercial execution is necessary, proven by an invoice addressed to the building owner." (p. 3, information sheet for the application BEG Residential Buildings Grant Efficiency House 461) Furthermore: "The invoices that must be kept must show the eligible measures, the work performed, as well as the address of the investment object and must be issued in German. Invoices for eligible measures must be paid cashlessly and the corresponding receipts (for example, bank statements) must be kept as proof of payment." (p. 11) Regarding energy efficiency experts: Their costs are subsidized at 50%, the consultant’s costs are capped at €5000, as far as I know.