KiDi Solar
Virtual Battery for Solar Panels in Spain
What a virtual battery is, what it costs, what it cannot do (it gives no power in a blackout) and how five major Spanish retailers compare, from an installer that does not sell electricity.
330+
Projects
5.0
3–5yr
Warranty
Surplus solar energy
What a Virtual Battery Is, and What It Is Not
A virtual battery is not a battery. It is a service from your electricity retailer: the solar energy you export and cannot offset on your bill is turned into a euro credit, which is then used on later bills. A sunny-month surplus can reduce a winter bill, but nothing is stored at your home.
KiDi Solar is the installer, not your electricity retailer. We size the solar system from your bill and your habits, we explain how each type of compensation works, and we tell you honestly when a physical battery makes more sense. The retailer contract is always your decision.
Quick facts
- It stores money, not energy: a credit on your future bills
- No equipment, no works and no space needed at home
- Offered by your retailer: terms, price and validity differ by company
- It does not supply power at night or during a power cut
It Is Not a Backup
If the grid goes down, a virtual battery gives you no electricity, because it only changes how your bill is calculated. Power during an outage needs a physical battery and an installation designed for backup. See Backup Power and Battery Storage.
How It Works
How a Virtual Battery Works
In three steps. The details change from one retailer to another, so always read the conditions of your own contract.
1. Your panels serve your home first
During the day the solar panels cover what your home is using at that moment. Only what is left over is exported to the grid.
2. The surplus becomes a euro credit
With normal simplified compensation, the surplus is deducted only up to the energy you bought from the grid in the billing period. With a virtual battery, the rest is not lost: it is saved as a balance in euros.
3. The balance reduces later bills
The balance is applied automatically to later invoices, so a sunny-month surplus can offset a winter bill. It normally cannot be paid out as cash.
Five Retailers Compared: Terms Checked in November 2026
We checked the published terms of five large Spanish retailers that offer a virtual battery. This is a map, not an offer: prices and conditions change, some are reviewed monthly, and the exact terms are in your own contract.
Iberdrola
Solar Cloud (part of Asistente Smart Avanzado) · source
- Surplus value
- Not published on the page
- Cost
- No price shown on the page
- Credit validity
- Not stated on the page (OCU reports 2 years)
- Good to know
- Credit goes to the energy term first, then the power term, then regulated costs. Usable on any of your contracts, including a second home.
Endesa
Solar Plus with Batería Virtual · source
- Surplus value
- €0.06/kWh (€0.0763 with 21% VAT)
- Cost
- €2/month
- Credit validity
- Not stated on the product page
- Good to know
- Installations up to 15 kW. No minimum term. Applies to the same supply point. Not compatible with Bono Social or PVPC.
Naturgy
Batería Virtual (Monedero Naturgy) · source
- Surplus value
- €0.06/kWh before taxes (€0.0726 with VAT); may be revised monthly
- Cost
- Advertised as €0, no activation cost, no minimum term
- Credit validity
- 5 years after the last bill that added to it
- Good to know
- Needs a Naturgy electricity contract with simplified compensation. Can be applied to electricity, gas and other supplies in your name. Not compatible with Tarifa Plana.
Repsol
Batería Virtual (Repsol Vivit app) · source · conditions
- Surplus value
- Set in the contract; no €/kWh figure on the product page
- Cost
- Not shown on the page (OCU lists Repsol among retailers charging €2–5/month)
- Credit validity
- No expiry
- Good to know
- Covers Repsol electricity and gas, and a second home with Repsol. If you cancel all your Repsol electricity supplies, the balance is lost.
Octopus Energy
Solar Wallet · source (third party)
- Surplus value
- €0.035/kWh, or €0.07/kWh if you also bought the installation from Octopus
- Cost
- Free
- Credit validity
- No expiry
- Good to know
- Covers the whole bill, including the power term. At most about 1,000 kWh per month goes into the wallet. We could not open Octopus’s own page, so check these figures with the company.
Checked on 11 November 2026 on the retailers’ own pages (linked), except Octopus, where the figures come from the comparison site TarifaÓptima (18 August 2026). Reported fees and expiry periods marked “OCU” come from the consumer organisation’s article on virtual batteries. Other retailers also offer a virtual battery; see our comparison of what ten retailers pay for surplus.
Virtual or Physical
Virtual Battery vs Physical Battery
They solve different problems, and they can work together. The physical-battery points below are general facts about home batteries; your own system is sized after a survey.
Virtual battery
- Stores the value of your surplus as a credit, not energy
- No equipment, space or maintenance
- No extra upfront cost; some retailers charge a monthly fee
- Does not power your home at night
- Gives no power during a blackout
- The credit stays with your retailer and contract: some retailers cancel it if you leave
Physical battery
- Stores energy to use in the evening and at night
- Reduces what you buy from the grid every day
- Many models can supply power during a power cut, if the installation is designed for backup
- Higher upfront investment and needs space
- Typical life of 10–15 years (Holaluz)
- Built for daily cycles, not for storing energy for weeks or months (OCU)
The two are complementary rather than alternatives: a physical battery covers daily cycles and backup, and the virtual battery credits the surplus the battery cannot store (OCU, Holaluz). If you need power during outages, only the physical battery does that: see our Backup Power service and our guide on whether a battery is worth it. For a side-by-side comparison and a decision checklist, read Virtual Battery vs Physical Battery in Spain. Planning panels as well? See solar panel installation.
What a Virtual Battery Costs
A virtual battery needs no equipment, so there is no installation cost. What it can cost is:
- A monthly fee. Endesa publishes €2/month; OCU reports fees of €2–5/month at some retailers; Naturgy and Octopus advertise it as free.
- A low surplus price. Most retailers value surplus at roughly €0.04–0.07/kWh, while the energy you buy costs roughly €0.12–0.22/kWh, so a kWh you use at home is worth two to three times a kWh you export.
- Contract rules. Validity of the credit, what it can offset, and what happens if you change retailer.
Illustration with round numbers: if your system exports 3,000 kWh a year at €0.06, the credit is about €180. If you use those same 3,000 kWh at home instead of buying them at about €0.15, you avoid about €450. This is an illustration, not a forecast. See how surplus compensation works.
How KiDi Solar Helps
KiDi Solar is the installer, not your electricity retailer, and we do not sell a virtual battery. We size the solar system from your bill and real habits, handle the legalisation and certificates, and explain which kind of compensation suits your consumption profile. If a physical battery is worth adding, or you need backup power, we tell you plainly. The retailer contract and the decision are yours.
Send us a recent bill and we will tell you which system size suits you and how much of your production you would use directly. Get a free estimate or call +34 677 307 907.
FAQ
Virtual Battery Questions Answered
It is a service from your electricity retailer. The solar surplus you export and cannot offset on your bill is saved as a euro credit that reduces later bills. Nothing is installed at your home and no energy is stored.
No. It is only a billing credit, so it gives no electricity when the grid is down. For power during an outage you need a physical battery with an installation designed for backup.
There is no equipment cost. Some retailers advertise it as free; Endesa publishes €2/month, and OCU reports €2–5/month at some retailers. The terms are in your retailer’s contract.
It depends on the retailer. Naturgy states 5 years after the last bill that added to it, Repsol states no expiry, and Octopus is reported to have no expiry. Iberdrola does not state it on its page; OCU reports 2 years. Check your own contract.
Generally no. The credit is applied to your bills, and Repsol’s conditions say it never creates a cash payment.
Not necessarily. A virtual battery suits you if you do not need backup and mostly want to use your summer surplus later. A physical battery makes sense if you want backup during outages or use a lot of electricity in the evening. The two can work together.
The credit belongs to your contract with that retailer. Naturgy sets the balance to zero when the contract with surplus compensation ends, and Repsol removes it if you cancel all your Repsol electricity supplies. Check this before you switch.
No. KiDi Solar is the installer, not an electricity retailer. We design and install the solar system and any physical battery, and we explain the options so you can choose the retailer yourself.
VIRTUAL BATTERY
Get the Most
From Your Solar
Surplus
Send us a recent electricity bill and we will tell you which solar system and battery setup fits your home, with a free survey and an individual quote.
- Solar surplus explained for your property
- System sized from your bill
- Physical battery and backup if you need them
- Legalisation and certificates handled
- Across the Costa del Sol
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Tell us about your property and your electricity use. Our team will contact you to arrange a free survey.