Choosing an electricity tariff when you have solar panels.

Responsible editor: Nicholas John Hopes, operator of Rayte.eu. This guide is for an existing or planned Spanish self-consumption system. Generation forecasts and supplier savings claims should be treated as estimates until measured; battery warranties should be checked against their written terms.

Solar splits one electricity profile into several flows. Some generation is used directly, some may charge a battery and some may be exported. The home still imports when demand exceeds available solar and battery discharge. A tariff comparison must price those flows separately.

1. Start with the grid, not the panel rating

Collect at least twelve months of grid import and export from the distributor or supplier. For a new system, estimate hourly production and consumption rather than subtracting annual generation from annual demand. A home can export at midday and still import heavily after sunset.

Record the shape of residual imports by hour or tariff period. That profile determines whether a flat, time-of-use or indexed import price is likely to fit.

2. Value direct self-consumption correctly

A solar kWh used immediately avoids buying a grid kWh at the applicable retail import cost. That avoided cost can be larger than the payment for exporting the same unit. Moving water heating, pool pumping, laundry or EV charging into sunny periods can therefore improve value without increasing panel output.

Do not value self-consumption at the headline export rate. It avoids a purchase; export creates a separate credit under the contract and legal mechanism.

3. Price the electricity still imported

Apply each candidate tariff to the measured or modelled residual import profile. Include every energy period, contracted-power term, regulated element, tax assumption, meter charge and compulsory service. Solar does not remove fixed power costs.

A tariff with cheap midday electricity may add little value if panels already cover midday demand. A lower evening or overnight rate may matter more for a solar home, especially with an EV or electric heating.

4. Add realistic export compensation

Multiply eligible exported kWh by the contract’s compensation method, then apply any billing-period limit and fees. Confirm whether the rate is fixed, indexed or variable, and whether unused value expires or can enter a supplier-specific virtual balance. Our virtual-battery guide explains the fees, expiry rules and billing limits to check.

Spain’s simplified compensation is an economic balance within the bill, not a promise of unlimited cash payment. Read the detailed surplus-compensation guide and the supplier terms.

5. Treat batteries as an operating system

A physical battery changes when electricity is imported and exported. Apply usable capacity, charge and discharge power, reserve level, round-trip losses and seasonal state of charge. A battery that is full before the strongest solar period can increase exports; a battery reserved for backup may reduce savings.

Some tariffs encourage cheap-grid charging. Test whether the import/export price spread exceeds energy losses and any cycling cost. Do not assume every daily cycle is free.

6. Compare contract features that affect solar

• Confirmation that the supply’s registered self-consumption arrangement is recognised.
• Export rate, index or formula and its review date.
• Billing-period credit limit and treatment of unused value.
• Virtual-credit fee, expiry, transfer and cancellation rules.
• Import prices in the hours when the home still uses the grid.
• Contracted-power prices and any maintenance bundle.
• Contract duration, minimum term and renewal method.

7. Run a full-year sensitivity test

Model sunny and weak-generation months. Test lower export, higher evening use and a period with the battery unavailable. If one tariff only wins under perfect production or aggressive export assumptions, the result is fragile.

Minimum annual solar-tariff model

Component	Treatment
Imported energy	Price by actual period
Contracted power	Include full annual cost
Services and fees	Include compulsory items
Export credit	Cap to usable contractual value
Taxes and meter	Use same assumptions

8. Verify the first bill after a change

Check the self-consumption notation, import periods, exported kWh, compensation rate, credit limit and any virtual balance. Align the supplier bill with distributor data and the contract. Missing compensation may be a registration or processing problem rather than a poor export month.

Official sources

• BOE — Royal Decree 244/2019 on self-consumption
• IDAE — practical self-consumption guide
• CNMC energy-offer comparator

Reviewed 28 August 2026. Confirm installation eligibility, registration and current commercial terms.