How Solar Panels Work in Spain

Solar panels generate electricity through the photovoltaic effect. Each panel contains dozens of silicon solar cells. When photons (particles of light) hit these cells, they knock electrons loose from silicon atoms, creating an electrical current. This is Direct Current (DC) electricity.

A crucial point that many people misunderstand: solar panels use light, not heat. This has two important implications:

• Panels work on cloudy days: Even behind clouds, diffused light reaches your panels. Production on a heavily overcast day in Málaga might be 10–25% of a clear day, but it is not zero. Light overcast or haze typically produces 50–80% of clear-sky output.
• Extreme heat actually reduces output: This is counterintuitive but important for Spain. Solar cells become less efficient as they get hotter. On a 40°C August day on the Costa del Sol, your panels may produce 8–12% less than on a clear 20°C day in March, even though there are more sunshine hours. This effect is measured by the panel's "temperature coefficient" — a good panel loses about 0.3–0.4% of output per degree Celsius above 25°C.

This is why spring months (March–May) often produce more total energy than you might expect relative to peak summer — the longer days and strong sun combine with cooler panel temperatures for optimal performance.

Your home, and every appliance in it, runs on Alternating Current (AC) at 230 volts and 50 Hz. But your panels produce DC electricity. An inverter bridges this gap, converting the raw DC from your panels into clean, grid-compatible AC.

The inverter also handles several critical functions beyond simple conversion:

• Maximum Power Point Tracking (MPPT): The inverter continuously adjusts the electrical load to extract the absolute maximum power from your panels as conditions change throughout the day.
• Grid synchronisation: Your inverter must produce AC that exactly matches the grid's voltage and frequency. If it does not, your system cannot export surplus energy.
• Safety shutdown: If the grid goes down, your inverter must immediately disconnect to prevent feeding electricity into lines that workers may be repairing.

Learn about the different types of inverter →

Once the inverter has converted your solar electricity to AC, it feeds directly into your home's electrical panel. From this point, something very important happens automatically: your home always uses solar electricity first, before pulling anything from the grid.

This is called self-consumption (autoconsumo in Spanish), and it is the single most valuable use of your solar energy. Every kilowatt-hour (kWh) you consume directly from your panels is a kWh you do not buy from your electricity company at full retail price (typically €0.12–0.18/kWh).

Common daytime loads that benefit from self-consumption include:

• Pool pumps: Running 6–8 hours during the day, these are perfectly matched to solar production. A typical pool pump uses 1–2 kW continuously.
• Air conditioning: Summer AC loads coincide with peak solar production. A split-unit AC running at moderate power uses 1–3 kW.
• Washing machines, dishwashers, dryers: Running these during the day (on a timer if necessary) directly consumes free solar power.
• Electric vehicle charging: If you have an EV, charging it during solar hours is one of the most cost-effective uses of solar energy. A 7 kW home charger can absorb most or all of your solar production.
• Hot water (with an electric boiler or heat pump): Heating your water tank during the day stores thermal energy for evening showers.

The golden rule: The more of your solar energy you consume directly, the better your financial return. Direct self-consumption saves you the full retail electricity price. Exported energy earns you only a fraction of that (see below).

When your home's electricity demand exceeds what your panels are producing — for example, on a cloudy morning, or in the evening after sunset — your home automatically and seamlessly draws the shortfall from the grid. This is called grid import.

You will not notice any interruption. The transition between solar and grid power is instantaneous and invisible. Your lights do not flicker, your appliances do not reset. The inverter and your smart meter manage everything automatically.

At night, when your panels produce nothing, your home runs entirely on grid electricity (unless you have a physical battery providing stored solar power).

This is why your electricity tariff still matters after solar. You will still import electricity from the grid, especially in the evenings and on cloudy days. Choosing the right post-solar tariff can save you hundreds of euros per year.

Find the best tariff after solar →

When your panels are producing more electricity than your home is using — typically mid-morning to mid-afternoon on a sunny day — the excess has to go somewhere. There are three possible destinations:

• Physical battery: If you have a battery installed, it will charge with the surplus energy, storing it for use in the evening or at night. Read about battery options.
• Grid export: If you do not have a battery (or your battery is already full), the surplus flows out through your meter into the grid. Your bi-directional smart meter records how much you export.
• Wasted: If your system is not properly legalised for surplus compensation, you may be exporting energy and receiving nothing for it.

How export compensation works in Spain: Spain uses a system called Compensación Simplificada de Excedentes. This is not net metering (where exported kWh offset imported kWh 1:1). Instead, your electricity retailer pays you a market-referenced price for each kWh you export (typically €0.05–0.08/kWh — significantly less than the €0.12–0.18/kWh you pay for imported electricity).

The export credit can offset your energy charges on each monthly bill, but it cannot offset fixed charges (like your contracted power fee, or término de potencia), and it cannot create a positive balance. If your export credits exceed your energy charges in a given month, the excess is lost.

This is why maximising self-consumption is so important: every kWh you use directly saves you €0.12–0.18, but every kWh you export earns you only €0.05–0.08.

Read our full guide to export tariffs →

After installation, your inverter's monitoring app will show you several numbers that can be confusing at first. Here is what each one means:

• Solar Production (kW / kWh): The real-time power output (kW) and total energy produced (kWh) by your panels. This number tells you how much electricity your panels are generating.
• Home Consumption (kW / kWh): How much electricity your home is using right now, and how much it has used in total.
• Grid Import (kW / kWh): How much electricity you are pulling from the grid. If this is zero during the day, your panels are covering all your needs.
• Grid Export (kW / kWh): How much surplus solar energy is flowing out to the grid. This is the electricity you will be compensated for.
• Self-Consumption Rate (%): The percentage of your solar production that you use directly. Higher is better — 60–80% is typical for a well-sized system without a battery; 80–95% with a battery.
• Self-Sufficiency Rate (%): The percentage of your total electricity consumption that comes from solar. This tells you how independent you are from the grid.

A common source of confusion: Your monitoring app shows solar production and your electricity bill shows grid charges. These are two different systems measuring two different things. Your bill will show imports minus export credits, not total consumption minus total production.