Quick Answer
Standard surplus compensation is limited by the value of grid energy consumed in the billing period. A virtual battery may carry extra credit forward under a separate commercial agreement; it is not physical storage or guaranteed cash income. Compare import prices and fees as well as export rates.
Exported electricity is not the same as a bill credit
Panels first contribute to consumption at the property. Electricity sent to the network is surplus export; electricity purchased when generation is insufficient is grid import. Compare distributor meter readings with billing dates, not just the generation total in the inverter app.
Under simplified compensation, eligible surplus receives a financial bill credit, not a one-for-one exchange of kWh or a cash payout. The credit is limited by the eligible imported-energy value in the billing period. A separate commercial credit account may offer additional benefits.
Where your solar electricity goes
Generation, home use and exports are different things.
Solar generation
Panels produce electricity. Compatible inverter equipment makes it usable in the home.
Home use
Electricity used while solar is generating can reduce what you buy from the grid.
Surplus export
Unused electricity can go to the grid. Its financial value depends on your tariff.
Optional physical battery
Can store energy for later use, within its charge, power and capacity limits.
Grid imports
The home still buys electricity when solar and available storage do not cover demand.
Concept illustration, not an installation wiring plan. Generation, self-consumption and exports are different measurements.
Worked example: what happens when exports exceed the cap?
Illustrative arithmetic, not a customer bill or a live tariff. Assume EUR 30 of eligible imported-energy charges and 800 exported kWh valued at EUR 0.05/kWh. The calculated export value is EUR 40, but simplified compensation is capped at the eligible EUR 30 for that period.
The remaining EUR 10 is not automatically paid in cash or carried forward. A virtual-battery contract may treat qualifying remaining value differently. Power charges, services, meter rent and taxes still need to be calculated: a zero energy subtotal is not a zero total bill.
Check the mechanism against Article 14 of Real Decreto 244/2019. Commercial benefits must be confirmed separately in your supplier contract.
Fixed or indexed export: compare the hours you actually export
Fixed export uses an agreed rate for the contracted period. Check its duration, revision provisions and whether it requires a particular import plan or paid service.
Indexed export follows the specified pricing formula. Ask for the index, deductions, settlement interval and treatment of negative prices. Do not assume every contract has a zero-price floor.
For an hourly offer, multiply each hour of metered exports by the applicable hourly rate, then sum the results. A headline wholesale average is not your achieved export rate. Historical data can explain a past result but cannot guarantee next year's prices.
The highest export price is not automatically the cheapest contract. Use our worked whole-tariff comparison to include import prices and other charges.
A virtual battery stores credit, not electricity
A virtual battery is a supplier-managed bill-credit account. It cannot power appliances during a blackout and is not a replacement for physical storage. A large displayed balance is only useful if the contract lets you spend it.
Two very different kinds of battery
Stored electricity is not the same as bill credit.
Physical battery
Electricity · kWh
Stores energy at your property for later use.
- Equipment and installation costs
- Capacity, power limits and losses
- Backup only with a compatible, correctly configured system
Virtual battery
Bill credit · EUR
A supplier account records financial credit under a commercial agreement.
- Check service fees and eligible bill charges
- Check expiry, transfer and cancellation rules
- No stored electricity and no blackout backup
Concept illustration. A physical battery provides backup only with compatible equipment and a correctly designed isolation arrangement.
- Which exported kWh qualify and how is their credit calculated?
- Which bill items can credits offset, and in what order?
- What fees, balance limits and expiry dates apply?
- Can another property use the balance, and must its contract holder match?
- What happens to unused credit when you switch or sell?
- Can import prices or credit terms change during the contract?
For an empty holiday home, model low-occupancy and occupied months separately. Do not size a system around credits that could expire before you need them. See the physical versus virtual battery comparison.
Exports appear in the app but not on the bill
First establish that the distributor records exports, rather than only seeing generation in the installer app. Then request installation registration evidence, distributor self-consumption status and the supplier compensation activation date. Check the supply point and billing dates match.
Use our high-bill troubleshooting checklist and missing export guide to organise a support request. Keep a case reference and a written explanation of any correction. Share unredacted bills only through trusted private support channels.
Evidence and comparison scope
Reviewed 10 September 2026 against the BOE self-consumption framework and Andalusian self-consumption guidance. No supplier is ranked here and no example represents an available offer.
For a commercial bill review, our partner weSwitchSpain provides tariff comparison support. Read our referral disclosure and ask which suppliers the comparison includes.