Solar PPAs in Spain: how an on-site PPA works and what to check before signing
With an on-site solar PPA in Spain, a financing partner pays for, owns and maintains a plant at your site, and you buy the power it produces. You pay nothing upfront and only for the kWh it supplies, at a price per kWh set in the contract that starts below what you pay the grid at signing and rises each year by a formula written into the contract.
What is an on-site PPA?
PPA stands for power purchase agreement, a long-term contract to buy electricity. On-site means the plant is at your premises: on the roof, over the car park or on adjacent land, connected to your electrical installation.
Spain’s self-consumption rules (Royal Decree 244/2019) allow the plant’s owner to be a different company from the one using the power. An on-site PPA relies on that: the financing partner pays for the plant and owns it, and you pay only for the kWh it supplies. Power the plant does not cover still comes from your retailer; your supply contract is adjusted for self-consumption, but you do not have to change company.
How is the price set, and why does it rise?
The starting price per kWh is set in the contract below what you pay the grid when you sign. From then on it rises each year by a formula written into the contract from day one: a set percentage, for example 2% a year, or an update linked to inflation (CPI). With CPI the increase follows actual inflation, which nobody knows in advance; with a set percentage it is known from the start and compounds, as the example below shows.
In one of our current projects, an agri-food business in Castilla-La Mancha that pays the grid about €0.15 per kWh would pay about €0.11 for the power of its plant. The bigger the plant, the lower the starting price tends to be, and power the site does not use is not lost: it can be credited on the bill or sold to the grid, as the contract sets out.
The price is predictable, because you know from the start how each year’s price is worked out, but it is not frozen. Nor can anyone tell you what grid power will cost in five or ten years: the Spanish wholesale price averaged about €65/MWh in 2025 and about €143/MWh in September 2026, its highest monthly level since 2022. Your starting price is known; each year’s saving depends on what you would otherwise have paid.
| Contract year | 2% a year | 3% a year |
|---|---|---|
| Year 1 | €0.090/kWh | €0.090/kWh |
| Year 5 | €0.097/kWh | €0.101/kWh |
| Year 10 | €0.108/kWh | €0.117/kWh |
| Year 15 | €0.119/kWh | €0.136/kWh |
| Year 20 | €0.131/kWh | €0.158/kWh |
Illustrative, not an offer. The price rises from year 2. At 2% a year, the year 15 price is almost 32% higher than at the start; at 3%, just over 51%. The example does not predict what grid power will cost in those years.
Who pays, who owns and who is responsible?
Each of these points should be written into the contract.
- The financing partner pays for the plant, owns it and handles maintenance, repairs and insurance for the whole term.
- You provide the site, roof or land, and buy the power the plant supplies at the contract price.
- Before signing, the financing partner checks your company’s credit, because it recovers its investment from your payments over many years.
- The term is set in the contract. Spanish law sets no minimum or maximum; market examples run from about 10 to 25 years, and a longer term usually allows a lower starting price.
- At the end of the term, depending on the contract, you can usually buy the plant, extend the contract or have the plant removed.
Who is an on-site PPA right for?
Businesses with steady daytime consumption that plan to stay at the site for years and prefer not to tie up capital in a plant, or that keep their investment budget for their own operations.
With Aeternus, PPAs start at 50 kWp. Below that size you can buy or lease the plant, which work at any scale.
A PPA fits less well if you may move soon, if the roof needs replacing within a few years or if your daytime consumption is set to fall sharply. Each can be handled in the contract, at a cost.
What should you check before signing?
A PPA runs for many years. Be clear on these clauses first:
- Term: how many years, and whether they run from signing or from switch-on.
- Starting price and increase formula: for a set percentage, which one; for CPI, which index, which month and whether there is a cap.
- What you pay for: only the power the plant supplies and you use, measured by a meter you can read.
- Surplus: what happens to power you do not use, whether it is exported, who earns from it and whether you are billed for it.
- Minimum purchase: whether you must pay for a minimum volume even if you use less, for example after dropping a shift.
- Output and breakdowns: what happens if the plant produces less than expected or stops, and how quickly it is repaired.
- Use of your roof or land: whether it is granted by a licence, a lease or a surface right, and who pays to remove and refit the plant if the roof needs work.
- Moving or selling the building: whether the contract can pass to a new owner or tenant, whether you can buy the plant early and what ending early costs.
- End of term: the price at which you could buy the plant, as a figure or a known formula rather than ‘market value’, and who pays for removal.
- Security: any guarantees, deposits or bonds requested, and when they can be called.
- Changes in the rules: what happens to the price if tolls, taxes or the self-consumption rules change.
PPA, buying or leasing: which is better?
The plant can be the same in all three. What changes is who invests, who carries the technical risk and how you pay.
If your company can invest, buying usually gives the larger saving over the plant’s life, because you do not pay a third party’s return. A PPA moves the investment and the technical risk to the financing partner, in exchange for paying for each kWh. Review the accounting and tax treatment of each option with your adviser.
| Aspect | Buy | Lease | PPA (from 50 kWp) |
|---|---|---|---|
| Upfront payment | The investment, from own funds or a loan | None or reduced, depending on the contract | None |
| Owner of the plant | Your company | The leasing company | The financing partner |
| What you pay | The plant and its upkeep | A set periodic instalment | Each kWh supplied, at a price that rises by the contract’s formula |
| Maintenance and insurance | Yours | Often included | The financing partner’s |
| If the plant produces less | You save less | You pay the same instalment | You pay less, because you pay per kWh |
| At the end of the term | The plant is still yours | Buy, renew or return, per the contract | Buy, extend or remove, per the contract |
How we arrange a PPA
We study your consumption and your site, size the plant and structure the deal with a financing partner and a vetted builder. You receive one proposal with the starting price, the increase formula, the term and the end-of-term options.
We never own the plant. We are paid a commission by the builder or financing partner we bring in, only if the project goes ahead, and you pay us no fee. For a first figure, buying or with a PPA, try the preview on our business page, or contact us: we reply within two working days. To choose the self-consumption arrangement first, read our guide to commercial solar in Spain; there is also a PPA guide in Spanish.
Questions
Is the price of a solar PPA fixed?
No. It is set in the contract below what you pay the grid at signing and rises each year by a formula written into the contract, a set percentage or CPI. It is predictable, because you know how it is worked out, but it is not frozen.
Who owns the plant under a PPA?
The financing partner. In Spain’s self-consumption register, if the plant does not export, you as the consumer are the holder of the installation; if it exports, the holder is the producer, which can be the financing partner.
Can I sign a PPA for a plant under 50 kWp?
Not with Aeternus. Below 50 kWp you can buy or lease the plant, and neither has a minimum size.
How is an on-site PPA different from an off-site PPA?
In an off-site PPA the plant is elsewhere, and you buy its output through the grid or settle a financial contract against the market price. Spanish off-site solar PPAs averaged about €31/MWh in the third quarter of 2026, according to LevelTen, but that buys energy only: tolls, charges and supply costs are still paid on every kWh. Self-consumed renewable power on site pays no tolls or charges.
Sources
- Real Decreto 244/2019, administrative, technical and economic conditions of electricity self-consumption (BOE, consolidated text, last updated 22 March 2026): https://www.boe.es/buscar/act.php?id=BOE-A-2019-5089
- Ley 24/2013 del Sector Eléctrico, article 9.5: self-consumed renewable energy is exempt from all tolls and charges (BOE, consolidated text): https://www.boe.es/buscar/act.php?id=BOE-A-2013-13645
- IDAE: Guía Profesional de Tramitación del Autoconsumo, v.6 (July 2024): https://libreria.miteco.gob.es/ebook/416/free_download/
- Cuatrecasas, Legal Flash Energía (November 2020): key points of PPAs, including contract term: https://www.cuatrecasas.com/resources/legal-flash-energia-claves-de-los-ppa-o-contratos-de-suministro-de-energia-renovable-a-largo-plazo-power-purchase-agreements.%20rd-ley%2024_2020-611f7f1586180923779452.pdf
- Acciona Energía: on-site PPAs for large business customers, typical terms: https://solutions.acciona-energia.com/en/empresas/autoconsumo/para-grandes-clientes
- Energías Renovables (20 February 2025): a 17-year on-site PPA for a 4 MWp self-consumption plant in Badajoz: https://www.energias-renovables.com/autoconsumo/veolia-badajoz-firma-un-snper-contrato-de-20250220
- CNMC: average annual day-ahead and intraday market price for 2025, €65.26/MWh: https://cnmc.es/sites/default/files/6367977.pdf
- Demócrata (October 2026): the Spanish pool averaged €143.26/MWh in September 2026, the highest since 2022: https://www.democrata.es/economia/el-encarecimiento-del-gas-y-la-demanda-disparan-el-pool-electrico-a-143-26-euro-mwh-en-septiembre-maximo-desde-2022/
- PV Tech (23 October 2026): LevelTen PPA price index, Spain solar PPAs averaged €30.93/MWh in Q3 2026: https://www.pv-tech.org/european-solar-ppa-prices-up-0-4-europe-4-9-us/