1. Identify what the price includes
List modules, inverter, mounting, access, roof work, electrical work, connection, procedures, testing and VAT. For roof integration, specify roof-covering functions and replaced work. Show battery, charging and backup separately. Two totals are not comparable when one excludes work or adds equipment absent from the other.
2. Calculate CHF/kWp correctly
Divide the selected amount by its corresponding capacity and state the scope. Deliberately chosen arithmetic examples: CHF 18’000 for 10 kWp equals CHF 1’800/kWp; CHF 24’000 for 8 kWp equals CHF 3’000/kWp. These are not a market survey or a promised quote. Compare work, equipment and expected results; the ratio alone does not identify the best offer.
3. Break down the net price
For each deduction, request the programme, calculation, conditions, documents and payment date. Separate the PV contribution, any local grant and tax effects. Confirm rules for combining grants and eligible expenses rather than subtracting generic grant and tax percentages. Keep a cash-flow schedule too: the estimated final net amount may differ from the funds needed at the start.
4. Relate price to usable energy
Request the site simulation and its losses, including shading, snow and downtime. Ask for monthly generation, on-site use and surplus. Snow does not automatically melt or slide in every layout; specify the assumption. Value savings using actual avoided tariffs and sales using the applicable contract. Annual kWh alone cannot promise winter heating or charging at any hour.
5. Compare service and lifetime costs
Include maintenance, insurance, finance, replacements and end-of-life charges in the options. Check the warranty provider, exclusions and service charges. For old equipment returns, distinguish return, dismantling, transport and collection. Compare less favourable generation and price scenarios too. A calculator and simple payback estimate inform the decision; they are not contractual commitments.