Guide · Switzerland
What battery size fits my goals?
Cooking dinner with electricity your roof produced earlier in the day is exactly what a home battery is for. But how much storage do you actually need? Your household’s daily routine tells you more than the panels’ specification sheet.
Short answerShort answer
What battery size fits my goals?
Night-time demand is a better starting point than PV capacity alone. More storage raises self-sufficiency, but not automatically the financial return.
What happens after sunset?
Look at the hours between the end of solar generation and the following morning. Do you cook, run a heat pump or charge a car then? An annual consumption figure cannot tell you that. If you already have solar, your monitoring data is a useful starting point: it shows when you export electricity and when you buy it back from the grid.
Extra capacity needs a job to do
A larger battery only helps if there is enough surplus to charge it and enough demand later to use that energy. Compare several sizes and look at what each step adds. Include a planned electric car or heat pump, but consider when it will run rather than treating it as an automatic reason to buy the biggest battery.
The key considerations
Always compare 5, 10 and 15 kWh with the same PV system and load profile. SwissEnergy cites about CHF 8,000 installed for a 15 kWh battery paired with a 12 kWp system; WattBilanz conservatively models 15 kWh at CHF 9,350.
Swiss price framework 2026
WattBilanz assumptions, September 2026: new PV CHF 5,700 fixed plus CHF 1,760/kWp; new battery CHF 2,300 plus CHF 470/gross kWh; retrofit CHF 4,300 plus CHF 470/kWh. Installation and VAT included, incentives excluded.
A worked example for Bern
The example is in Bern (postcode 3011): a 10 kWp south-facing system on a 30° roof, serving a four-person household using 4,050 kWh a year. Imported electricity is priced at 32 ct/kWh. Exports receive 6 ct/kWh for energy plus 1.5 ct/kWh for guarantees of origin. The Pronovo grant is included; local grants, a heat pump and an EV are not.
The PVGIS model estimates annual generation at 12,232 kWh. Each battery size is compared with the same PV system without storage. The 20-year result is the battery’s additional economic contribution after its estimated cost, not the overall result of the PV system.
| Gross battery capacity | Estimated cost | Additional annual benefit | Additional 20-year contribution |
|---|---|---|---|
| 5 kWh | CHF 4,650 | CHF 367 | CHF 2,698 |
| 10 kWh | CHF 7,000 | CHF 550 | CHF 3,991 |
| 15 kWh | CHF 9,350 | CHF 576 | CHF 2,170 |
| 20 kWh | CHF 11,700 | CHF 579 | CHF −119 |
The annual benefit grows only slightly from 10 to 15 kWh, while the larger battery costs more. At 20 kWh, the additional contribution is slightly negative in this simplified model. More self-sufficiency does not automatically mean a better financial result.
What the built-in optimizer shows
The built-in optimizer tests capacities from 0 to 30 kWh and seeks the highest additional economic result over 20 years, not maximum self-sufficiency. For this Bern example, the maximum is at 9 kWh gross capacity. Options from 7 to 11 kWh reach at least 90% of that maximum and are treated as nearly equivalent economically.
| Capacity | Self-sufficiency | Self-consumption | Annual savings | Result after 20 years | Payback |
|---|---|---|---|---|---|
| 7 kWh · 90% lower bound | 87.3% | 30.7% | CHF 466/year | CHF 3,734 | 12.0 years |
| 9 kWh · optimum | 93.7% | 33.1% | CHF 528/year | CHF 4,034 | 12.4 years |
| 10 kWh · selected | 95.9% | 33.9% | CHF 550/year | CHF 3,991 | 12.7 years |
| 11 kWh · 90% upper bound | 97.3% | 34.4% | CHF 563/year | CHF 3,780 | 13.3 years |
The calculation peaks at 9 kWh, but I would also consider the near-equivalent range. For this example, I would lean toward its upper end: greater self-sufficiency gives me more breathing room if electricity prices change. That is my personal trade-off, not a price forecast.
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
Keep your PV system and consumption unchanged, then try different battery sizes. Look at what the extra capacity adds, not just the final self-sufficiency figure.