A battery stores the energy your panels produce during the day and you do not use, so you can use it at night. It sounds perfect, but it does not always pay off. It depends on when you use your electricity.
When a battery is worth it
- You use a lot of power in the evening and at night: families out during the day, air conditioning at night in summer, electric cooking in the evening.
- You have a lot of surplus that your supplier credits at a low price, or that is lost because there is nothing left on the bill to offset.
- You want power during a blackout. A battery alone is not enough for that: you also need a backup system. See do solar panels work in a power cut?.
- You want the Junta de Andalucía incentives: the residential scheme that opened in October 2026 requires home solar systems to include storage (Energías Renovables, 22/10/2026).
When it is not
- You are at home for much of the day and already use most of what the panels produce.
- Your night-time use is small (fridge, router and little else).
- Your budget is tight. It is often better to start without a battery and with a hybrid inverter so you can add one later.
How to choose the capacity
Battery capacity is measured in kWh. A practical rule is to size it for your real night-time consumption, not for the size of the panels:
- Look at how much you use between sunset and morning. We can read it from the hourly data of your distribution company.
- Choose a battery that covers that most days.
- Remember it is not discharged to 100 %: usable capacity is a little lower than the rated figure.
A battery that is too big sits half-charged in winter and never pays for itself. One that is too small is empty by midnight.
Physical battery or virtual battery
Some Spanish electricity suppliers offer a virtual battery (batería virtual). They keep, in euros, the value of the surplus they cannot credit to you that month and take it off future bills. It does not give you power in a blackout and stores no energy, but it can be a cheap alternative if your surplus is large. Read the conditions carefully: there are often fees or expiry dates.
A real example
On this home in Valle Niza we installed 10 kW of panels with a 16 kWh battery, because the family uses a lot of power in the afternoon and at night.
Not sure whether you need a battery? We will run the numbers with your bill, in English: use our bill check or see solar panels with batteries.