Putting solar panels on your Spanish home (autoconsumo)

Terms used

• Autoconsumo — Autoconsumo is producing your own electricity, here with solar panels, and using it in your home.
• Declaración responsable — A declaración responsable is a simple notice to your town hall that you are doing works, instead of waiting for a licence.
• ICIO — The ICIO is a municipal construction tax charged on the cost of works.
• IBI — The IBI is the yearly municipal property tax.

Key rules

• Surplus credit: Surplus energy is credited on your bill at the price your retailer offers, but the credit can never exceed what you pay for energy taken from the grid, so it cannot produce a payment.
• Simplified compensation: Simplified surplus compensation is available for renewable installations of 100 kW or less with a single supply contract.
• Grid permits: Installations of 15 kW or less on urban land do not need access and connection permits.
• Battery: A battery behind your meter is allowed and does not trigger a sun tax.

How home solar works

Solar for your own use is called autoconsumo. Your panels power your home first. You can choose a system with no surplus or one with surplus, and you can install it for one home (individual) or share it with neighbours (collective).

• Without surplus: a device stops any power going to the grid. It is the simplest setup, but you earn nothing from extra production.
• With surplus: extra power goes to the grid. You can then either take the simplified compensation or not.

What happens to surplus

Under simplified compensation, your retailer credits the surplus you send to the grid against your bill. It does this for each billing period, which can be at most one month. The price is whatever your retailer offers, usually linked to the hourly wholesale price.

The credit can never exceed what you pay for energy taken from the grid, so it cannot produce a payment. Fixed charges, grid tolls and taxes are not reduced. Some retailers carry unused credit forward as a "virtual battery". Terms vary, so compare retailers.

To qualify for simplified compensation you need:

• a renewable source,
• a total of 100 kW or less,
• a single supply contract,
• no other remuneration scheme for the generator,
• a surplus compensation contract with your retailer.

Shared solar

Neighbours can share one installation, for example on a community roof. Installations must be close to the homes they supply. The usual limit is 500 m, and in some cases it is longer. Ask your electricity distributor which limit applies to you before you commit.

Should you add a battery?

Batteries are allowed and count as part of your installation. A battery behind your meter does not make you pay a "sun tax". Your installer must include it in the technical project and the electrical certificate. A battery added later is a modification. Notify your region and distributor, and check the procedure with your regional industry department. The decision block below helps you weigh the choice.

Permits and registration

• Grid permits: installations of 15 kW or less on urban land do not need access and connection permits.
• Town hall: in most cases a declaración responsable is enough, not a full works licence. Protected buildings or works that affect the structure may need more, so ask your town hall.
• Region: your installer prepares the technical project, issues the low-voltage certificate and registers it with your regional industry department. The region then records the installation in the regional and national registers.
• Distributor and retailer: notify the distributor and sign the contract modification. If you want surplus credit, sign the compensation contract with your retailer.

The steps in order, and the documents, are in the blocks below.

What it costs

Quotes are usually given per kWp (kilowatt-peak, the panel capacity). Bigger systems cost more in total but less per kWp. A battery adds a significant amount, often as much as the panels themselves. Price depends on installer, roof, inverter and region, so get several quotes with and without a battery.

On top of that, expect the construction tax (ICIO), a municipal tax of up to 4% of the works cost. Some towns also charge a licensing fee. Many towns reduce the ICIO by up to 50% for solar, and some cut the IBI property tax for several years. Rates and rebates differ by town hall.

Grants and payback

Grants depend on your region, and many earlier calls have closed. Ask your regional energy agency what is open now. Many calls require you to apply before you start work.

Typical payback without a battery is 4 to 8 years. With a battery it is usually longer, often above 8 years. Your own consumption and tariff decide the real figure. Use the payback estimator below.

Choosing between options

Should you add a battery to your solar panels?

• Panels only: You use most of your power during the day. Payback is usually around 4 to 8 years.

• Panels with a battery: You use most power in the evening and accept a longer payback, often above 8 years and sometimes 10 or more. A battery often costs as much as the panels.

Choose panels only if you use power mainly during the day or want the shortest payback. Add a battery if evening use is high and an open regional grant lowers its cost.

Payback and grant availability depend on your home, tariff and region; check them with installers and your regional energy agency.

Installing solar step by step, from quote to registration

• Have an installer survey your roof or site: orientation, shade, structure and electrical connection: First, before you ask for prices

• Get several quotes and choose the system type: individual or shared, with or without surplus compensation: After the survey

• If you live in a flat and want shared solar on the roof, put it on the community meeting agenda. It needs a simple majority of owners at the meeting. Your community administrator handles the meeting.: Before any work starts

• Check which grants are open with your regional energy agency. Many grant calls require you to apply before works start or a contract is signed, so read the call before committing.: Before you sign a contract

• Tell your town hall about the works with a declaración responsable (a simple notice). Pay the construction tax (ICIO). A licence is needed only for protected buildings or works that affect the structure.: Before the installation starts

• Sign the contract with the installer and have the system installed. An installer prepares the technical project or design memo.: After the vote, grant application and town hall notice

• Have the low-voltage electrical certificate registered with your regional industry department. The region then records the installation in the national self-consumption register (RADNE) itself.: Right after the installation is finished

• Notify your electricity distributor (the company that owns the grid and meter) and sign the contract modification. Installations of 15 kW or less on urban land need no access and connection permits.: After the certificate is registered

• Sign the surplus compensation contract with your electricity retailer: Before you start sending surplus to the grid

• Ask your town hall for construction tax or property tax rebates, and keep your invoices for any grant: After completion, within the time your town hall sets

Documents you need

• Technical project or technical memory (memoria técnica de diseño), prepared by your installer. If you add a battery, it must be included.

• Low-voltage electrical installation certificate, issued by your installer and registered with your regional industry department.

• Surplus compensation contract with your electricity retailer, needed if you want surplus energy credited on your bill.

• Contract modification with your electricity distributor, the company that owns the grid and meter.

Checklist

• Decide whether you want a system with or without surplus, and check that your installation fits the simplified compensation conditions.

• Ask your town hall whether a declaración responsable (a simple notice) is enough, especially if your building is protected or the works affect its structure.

• Ask your regional energy agency which grants are open for solar and batteries.

• Check with your electricity distributor the distance limits if you plan shared solar with neighbours.

• Confirm with your regional industry department that your installation is registered, including any later battery.

Estimate your solar payback

Work it out

What you enter

• System size you are quoted (kWp): The installer's quote, listed as kWp (peak power).
• Total installed price (EUR): The total on the installer's quote, including the inverter and fitting.
• Yearly output per kWp at your address (kWh): Use the PVGIS tool for your address, or ask the installer. Typical values run from about 1,100 on the north coast to 1,800 in the south.
• Share of the solar energy you use yourself at home (%): Ask the installer to estimate it from your daytime use. It is higher if someone is home during the day.
• Price you pay per kWh bought from the grid (EUR/kWh): Your electricity bill, energy price per kWh.
• Price your retailer pays per kWh of surplus (EUR/kWh): Your retailer's surplus compensation offer on its website.
• Grants and rebates you will actually receive (EUR): The regional energy agency for grants, and your town hall for construction tax or property tax rebates. Enter 0 if none are open.

Worked example (with System size you are quoted 5 kWp, Total installed price 6,000 EUR, Yearly output per kWp at your address 1,500 kWh, Share of the solar energy you use yourself at home 40 %, Price you pay per kWh bought from the grid 0.18 EUR/kWh, Price your retailer pays per kWh of surplus 0.05 EUR/kWh, Grants and rebates you will actually receive 0 EUR)

When the sum misleads

• Surplus credit can never be more than what you pay for energy taken from the grid, so cap the surplus credit at your yearly grid energy cost if it comes out higher.
• A battery raises the share you use yourself but adds a large cost, often as much as the panels, so payback is usually longer. Add the battery to the installed price and raise the self-use share.
• Shaded or badly oriented roofs produce less than the typical yield. Use a lower yield figure if your installer says so.
• If no grant is open, enter 0. Do not count a grant you have not been awarded.

Frequently asked questions

Can I add a battery to my solar panels later?

Yes, you can add a battery later, but it counts as a modification of your installation. You must notify your region and your electricity distributor, and the battery has to be included in the technical documentation. Procedures vary by region, so ask your regional industry department.

How long does it take for home solar to pay for itself?

A home solar system without a battery usually pays for itself in around 4 to 8 years. With a battery it is usually longer, often above 8 years and sometimes 10 or more. The result depends on how much of the power you use during the day, where you live, your electricity price and any rebates.

Are there grants for home solar panels and batteries right now?

Whether a grant is open now depends on your region, because many of the EU-funded calls have closed or run out of money. Town hall rebates on the construction tax and the IBI property tax may still exist.

Does my battery make me pay a sun tax?

No, a battery behind your meter does not pay any sun tax. It is treated as storage inside your installation, not as a separate generator.