Guide · Switzerland
How large should my PV system be?
Your electricity bill describes life today. The panels on your roof also need to make sense for the way you may live in the future. Choosing their size deserves a longer view than the next annual bill.
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How large should my PV system be?
Use suitable roof areas well. A heat pump, electric car and future electrification often argue against sizing only for today’s consumption.
Consider the roof and your plans together
You may be thinking about a heat pump or an electric car. Those plans can support using more of the roof, but they do not replace a proper assessment of it. An accessible, sunny section is different from a heavily shaded corner that would be expensive to equip.
Ask what the extra panels cost
Once scaffolding, planning and electrical work are already part of the project, a useful question is how much the larger version adds to the bill. Request a smaller and a larger layout with comparable scope. Compare the extra cost with the extra generation rather than assuming that either the smallest or the largest system must be best.
The key considerations
The SFOE price study shows clear economies of scale: small systems cost more per kWp. Grid connection, structural checks, fire protection and any self-consumption community should be clarified early.
A Bern example: 5, 10 and 15 kWp
All three options are in Bern (postcode 3011) and serve the same four-person household using 4,050 kWh a year. South orientation, a 30° roof pitch, a 10 kWh battery and tariffs stay the same. Only PV capacity changes. The model excludes a heat pump, EV and local grants.
| PV capacity | Generation/year | PV self-consumption | Household demand covered | Grid imports/year | Grid exports/year | Net investment | Result after 20 years |
|---|---|---|---|---|---|---|---|
| 5 kWp | 6,116 kWh | 59.8% | 3,439 kWh · 84.9% | 611 kWh | 2,461 kWh | CHF 19,700 | + CHF 6,001 |
| 10 kWp | 12,232 kWh | 33.9% | 3,886 kWh · 95.9% | 164 kWh | 8,088 kWh | CHF 26,700 | + CHF 10,301 |
| 15 kWp | 18,348 kWh | 22.9% | 3,933 kWh · 97.1% | 117 kWh | 14,155 kWh | CHF 33,700 | + CHF 12,702 |
The PV self-consumption share falls as capacity increases because more electricity is exported. Even so, the additional generation has economic value in this model. The 15 kWp option delivers the highest 20-year result here, at about CHF 12,702. The largest step is from 5 to 10 kWp, but expanding to 15 kWp remains the most economical option in this specific comparison. The result depends on these assumptions and is not a return guarantee.
Official and specialist sources
- SFOE: photovoltaic market – 2025 price study
- ElCom: electricity tariffs 2026
- Pronovo: one-off payment calculator
- SwissEnergy: home battery storage
- SwissEnergy: self-consumption
- European Commission: PVGIS
- WattBilanz: Pronovo, exports, guarantees of origin and tax
Sources and price assumptions last checked on 18 September 2026.
Continue with your own data
Compare suitable roof sections and add a second scenario for specific changes you are planning to your heating or transport.