Almost every home solar system in Spain works the same way: the panels supply the house, the grid stays connected, and electricity flows in whichever direction is needed at that moment. Spanish law calls this autoconsumo, self-consumption. This guide explains how the power flows, which type of self-consumption most homes use, and how a system is registered. How exported power is credited on your bill has its own guide: selling excess solar electricity in Spain.
How the power flows
1. Panels turn daylight into direct current (DC). 2. The inverter converts it to alternating current (AC) at the voltage and frequency of the grid. 3. The house uses that power first. Whatever is switched on, the fridge, the air conditioning, the pool pump, runs on solar power as long as there is enough. 4. If the panels produce more than the house uses, the surplus flows out to the grid through your meter. 5. If the house uses more than the panels produce, at night or on a dull day, the difference comes from the grid, as before.
Nothing needs switching. The meter records what goes in each direction, hour by hour.
A day on a sunny roof
- Early morning: the panels start slowly. The house still draws mostly from the grid.
- Late morning to mid-afternoon: production is at its highest. The house runs on solar power and the surplus goes to the grid.
- Evening: production falls away just as cooking, lights and often air conditioning start. The house draws from the grid again, or from a battery if there is one.
That is why using power in the middle of the day, with timers on the pool pump, dishwasher or washing machine, gets more out of the same panels.
The three types of autoconsumo
The Spanish regulation for self-consumption (Real Decreto 244/2019) sets out three types:
- Without surplus (sin excedentes). A device prevents any power from going to the grid. The system is simpler to process, but any surplus is lost.
- With surplus, under compensation (con excedentes acogida a compensación). The surplus goes to the grid and is credited on your electricity bill each month. This is what most homes use.
- With surplus, not under compensation. The surplus is sold as a producer under the general rules for electricity production. This is rarely worth the extra administration for a home.
To use simplified compensation, the system has to be renewable, have an installed power of no more than 100 kW, and you need a compensation agreement with your electricity company. For solar, installed power means the power of the inverter, not the panels.
Is a battery needed?
No. A grid-connected system works without one: the grid covers what the panels do not. A battery can store daytime surplus for the evening; see do you need a solar battery in Spain.
What happens in a power cut
A grid-connected system switches off when the grid fails, for the safety of people working on the lines. Keeping power during a cut needs a back-up system; see do solar panels work during a power cut.
How the system is registered
A home system does not stay informal. In the Valencian Community, after installation the authorised installer files the installation online with the regional industry department: with a technical design document (memoria técnica de diseño) for systems up to 10 kW, or with an engineer’s project above that. The region then registers the self-consumption installation itself and informs the distributor, which updates your access contract. You do not have to file anything yourself for a normal home system. The retailer then sets up the compensation agreement.
Home systems with surplus up to 15 kW on urban land, and all systems without surplus, are exempt from the separate grid access and connection permits that larger generators need. Separately from all of this, the town hall has to be informed. The detail, and who does what, is in what documents you need for a solar installation.
Words you will come across
The table below explains the Spanish terms that appear on quotes, bills and paperwork. For how we design and install a system like this, see solar panel installation.
