Build the project around your property and electricity use. Treat funding, connection and installation as separate items to confirm.
Prepare one brief for every installer
Gather your annual electricity use, roof information and any plans for an electric vehicle or heat pump. Ask for a site visit and a clearly stated generation estimate. Separate current consumption from future purchases so the proposed system is not justified only by equipment you may never install.
Compare the full installation
Ask each company to identify its responsibilities for scaffolding, the meter cabinet, electrical work, grid coordination and handover. Use the Verbraucherzentrale planning guide as a reference when preparing questions. Do not assume all enabling work is included in a headline price.
Keep finance visible
KfW publishes information on photovoltaic financing. Check the current product and application conditions before relying on it, and distinguish a loan from a grant. Local offers can differ; make a written list of confirmed support rather than subtracting assumed funding from your budget.