Is a battery worth it with a solar system? The calculation

The calculation in detail so you can check it: purchase price divided by the electricity that flows through the battery over its life. CHF 6,860 for 10 kilowatt-hours (median price from the SFOE price survey 2025 for batteries below 10 kWh, excluding VAT), of which 9 kilowatt-hours are usable at 90 percent depth of discharge, 250 full cycles per year over 10 warranty years gives 22,500 kilowatt-hours and therefore around 30 centimes per kilowatt-hour. Over 15 years it is around 20 centimes. You can replace every one of these assumptions with the figures from your own quote – and that is exactly what you should do before someone else does it for you.

The benefit is smaller than it looks: you do not save the full electricity price, only the difference between what you pay for grid electricity and what you would have received as a feed-in payment for the same kilowatt-hour. Each grid operator sets that payment itself within the framework of the Energy Act, and it varies considerably across Switzerland. The pvtarif.ch tariff overview run by the association of independent energy producers shows your local value. If your feed-in price is high, the battery advantage shrinks; if it is low, it grows. Without that single figure, every battery calculation is guesswork.

Self-consumption also works without a battery – and that is the cheaper half of the answer. According to EnergieSchweiz, over a year a single-family house covers about 30 percent of its consumption with its solar system without further measures, around 50 percent with a controlled heat pump and electric mobility, and up to 70 percent with a battery. At the same time, according to calculations by the Swiss Federal Office of Energy, a new system is on average economical from a self-consumption rate of 35 percent – a threshold that can in most cases be reached with an energy management system alone. Swissolar’s technical information cites self-consumption shares of up to 90 percent for batteries; the two figures do not necessarily contradict each other, because the actual share depends heavily on the consumption profile and system size, but 90 percent is a best case and not an expectation.

Prices have fallen sharply, but waiting longer gains little. The SFOE price survey 2025 reports a median price of CHF 686 per kilowatt-hour for batteries below 10 kilowatt-hours and CHF 504 for 20 to 30 kilowatt-hours – in each case as part of a new installation where planning, logistics and administration are shared with the solar system. The Swissolar battery monitor 2026 arrives at around CHF 586 per kilowatt-hour for a typical 15 kilowatt-hour home battery including material and labour, i.e. about CHF 8,800; a year earlier the same battery cost around a quarter more. Swissolar, however, no longer expects strong further price cuts but a market stabilisation in the home storage segment.

Since January 2026 the framework has shifted in favour of batteries without reversing the calculation. Payment for electricity fed into the grid is now based on the quarterly averaged market price at the time of feed-in, with minimum payments for systems below 150 kilowatts (Article 15 paragraph 1bis of the Energy Act, in force since 1 January 2026). Grid operators may limit feed-in at the connection point as long as no more than 3 percent of annual production is lost – but electricity that is not fed in can still be self-consumed or stored. And for electricity drawn from the grid, stored and fed back in, a refund of the grid usage fee can be applied for since 1 January 2026; the Swissolar battery monitor 2026 nevertheless considers the required metering and delimitation rules to be very demanding.

Warranty is not service life, and both are in the data sheet – if you read it. According to Swissolar fact sheet no. 13, manufacturers frequently offer a warranty period of ten years or a specified number of full cycles, whichever is reached first; a permanent internet connection can be a precondition for warranty cover. The data sheet example there also shows how quickly figures are misread: 5.0 kilowatt-hours of nominal capacity yield only 4.5 usable kilowatt-hours at 90 percent depth of discharge, the system warranty is 7 years, and what is often guaranteed is 80 percent residual capacity at the end of that period. The inverter has its own, usually shorter periods than the cells. Get these four values – usable capacity, full cycles, warranty period, warranty conditions – in writing before you sign.

Not every reason for a battery has to be financial, and that is not an excuse. Swissolar fact sheet no. 13 already noted in 2022 that owners today decide on a storage system for reasons other than economic ones; the 2026 battery monitor lists interest in the technology, the integration of electric mobility and possible backup power alongside self-consumption as frequent motives for residential buildings. Anyone who wants to draw less electricity from the grid, who is planning a heat pump and an electric car, or who simply wants to use more of their own electricity, is making a legitimate decision. It only becomes more honest when it is named as such – and not sold as a return.