A virtual battery stores money on your electricity bill. A physical battery stores energy in your home. The first costs little upfront but does nothing in a blackout; the second costs more but powers your house in the evening and when the grid fails.
This guide compares the two for homes on the Costa del Sol: what each does, what it costs, where each one loses money, and how to choose.
Quick answer
- €0 upfrontVirtual battery: no equipment, though some retailers charge a monthly fee
- From €2,000KiDi Solar price of a 16 kWh physical battery
- 10–15 yearsTypical life of a home lithium battery
- FreeCalculation from your real electricity bill
What each one actually is
A virtual battery (batería virtual) is an accounting feature offered by some electricity retailers. Surplus solar you export to the grid is converted into euros of credit, and that credit is used to reduce later bills, for example in winter. No energy is stored. Details differ by retailer; we compared Iberdrola, Endesa, Naturgy, Repsol and Octopus on our virtual battery page.
A physical battery is a lithium storage unit connected to a hybrid inverter. It charges from your panels during the day and supplies the house in the evening and at night. With a backup-capable inverter it can also keep chosen circuits running when the grid is down. See battery storage.
Side by side
| Virtual battery | Physical battery | |
|---|---|---|
| What it stores | Euro credit on your bill | Electricity (kWh) |
| Upfront cost | None; a monthly fee on some plans | From €2,000 for 16 kWh, plus inverter and installation as quoted |
| Power cut | No help | Backup possible with the right inverter |
| Evening and night use | You still buy from the grid, offset by credit | Served from your own stored solar |
| Contract dependence | High: credit lives with one retailer and can expire or be lost | Low: the equipment is yours |
| Space needed | None | Wall or floor space in a garage or technical room |
| Typical life | As long as the contract | 10–15 years |
Where a virtual battery loses money
Retailers usually pay for surplus at a low price and sell you energy at a higher one. In our comparison of ten retailers, surplus was mostly paid at around €0.04–0.07 per kWh, while energy bought from the grid costs roughly €0.12–0.22 per kWh. Credit turns your exports into a discount on the bill, but each kWh is valued at the lower surplus price.
Example: 3,000 kWh exported at €0.06 gives about €180 of credit. If the same 3,000 kWh were stored and used in the evening instead of buying at about €0.15, it avoids about €450. These are illustrative figures; your numbers depend on your tariff and consumption.
Other limits to check in the small print: monthly fees, credit that expires (Naturgy lists 5 years), credit that is lost if you cancel all supplies with the retailer (Repsol), caps on power or monthly kWh, and plans that exclude the regulated PVPC tariff.
Where a physical battery loses money
- Upfront cost. A 16 kWh battery starts from €2,000, and the final quote depends on inverter compatibility, backup wiring and electrical work.
- Payback depends on your evening use. A home that is empty most of the year has little to store. See is a battery cost-effective for my PV system.
- Space. It needs a suitable location and ventilation as specified by the manufacturer.
- Ageing. Capacity declines over its 10–15 year life.
Power cuts: the one real difference
A virtual battery is credit on a bill. If the grid fails, a house with only a virtual battery has no power, even with a large balance. A standard solar system without a battery also shuts down during an outage, as the inverter disconnects for safety. Only a hybrid inverter with a battery can supply the house during a grid failure, on the circuits you choose or the whole house. See backup power.
Large outages are rare but they happen: on 28 April 2025 a blackout hit most of Spain and Portugal, starting shortly after 12:30 and lasting until nightfall, with power fully restored the next day, according to Euronews’ report on the government findings. Whether backup is worth paying for is your decision; it is the main reason owners choose a physical battery.
Using both
The physical battery covers your evenings and nights first. Surplus that still goes to the grid once the battery is full can build credit with a retailer that offers a virtual battery. Note that OCU points out that with a physical battery you accumulate less virtual credit, so check that the credit is worth having before choosing a plan around it.
Which one should you choose?
A virtual battery may be enough if:
- The house is a holiday or second home, used mostly in summer.
- You want to keep the upfront budget for panels only.
- You do not need power during an outage.
A physical battery is worth considering if:
- You live here year-round and use A/C, appliances or pool heating in the evening.
- You want security, internet and refrigeration to keep running in an outage.
- You want to buy as little grid electricity as possible.
How KiDi Solar helps
We do not sell electricity, so our advice is independent. We take your real electricity bills, look at your consumption pattern and tell you whether a physical battery pays off in your case or whether surplus compensation or a virtual battery is enough. The calculation is free. Start with the solar panel calculator or contact us. To understand how surplus is valued in the first place, read how surplus compensation works; if you do not have panels yet, see our solar panel installation service.
FAQ
Does a virtual battery work during a power cut?
No. A virtual battery is a credit on your electricity bill, not equipment in your home. If the grid goes down, so does your house, whatever the balance says. Backup needs a physical battery and a backup-capable hybrid inverter.
Is a virtual battery free?
Usually there is no equipment cost. Some retailers charge for it: for example Endesa lists €2 per month on its Solar Plus plan, and others build it into the tariff. We checked the offers in November 2026; terms change, so confirm with your retailer.
Can I have both a virtual and a physical battery?
Yes. The physical battery covers your evening and night use first; surplus that still reaches the grid can build credit with a retailer that offers a virtual battery. OCU notes that with a physical battery you will accumulate less virtual credit, so the combination only makes sense if your plan keeps the credit valuable.
How long does a physical battery last?
Typically 10 to 15 years for home lithium batteries, depending on the model, usage and warranty. Check the manufacturer’s warranty terms.
How much does a home battery cost with KiDi Solar?
A 16 kWh battery starts from €2,000. The final quote depends on inverter compatibility, backup wiring and the electrical work needed.
Which is better for a second home?
Often a virtual battery or simple surplus compensation, because there is little evening use to store. A free calculation from your real bills answers it for your house.
Free calculation for your home — Contact KiDi Solar
Sources
- KiDi Solar: virtual battery retailers compared (official retailer pages, checked November 2026)
- KiDi Solar: surplus prices by retailer
- Euronews, 17 June 2025
- OCU and Holaluz articles on virtual batteries; Endesa blog