A solar farm or battery site doesn’t just “sell electricity”. It can earn from several markets, sometimes at the same time. Here is how it works in Great Britain, in plain English.

Solar farms: mostly long-term contracts

Solar makes power when the sun shines, so most solar farms sell it on long, fixed terms:

  • Contracts for Difference (CfD). A government-backed contract that guarantees a fixed price for 20 years. In the latest round (results February 2026), solar won about 4.9GW of contracts at around £65 per MWh (in 2024 prices).
  • Power purchase agreements (PPAs). A fixed-price deal with a business or energy supplier, often for 10 years or more. See what is a solar PPA?
  • Selling at market prices. Some sites sell some or all of their power at the going rate. That is riskier, as prices move.

Battery sites: buy low, sell high, and help the grid

Batteries can charge when power is cheap and plentiful, and discharge when it is scarce and expensive. They can also respond in under a second to keep the grid stable. That gives them several ways to earn:

  1. Wholesale trading. Buying and selling power in the day-ahead and intraday markets. This is now the biggest source of battery income.
  2. The Balancing Mechanism. The system operator, NESO, pays sites to raise or lower output at short notice to keep supply and demand matched.
  3. Frequency response. Fast services such as Dynamic Containment, Moderation and Regulation, which steady the grid’s frequency after a sudden change.
  4. Reserve. Newer services, Quick Reserve and Slow Reserve, that pay sites to be ready to help within minutes.
  5. The Capacity Market. Payments for being available when the grid is tight. The latest four-year-ahead auction cleared at about £27 per kW per year.
  6. Local flexibility. Network operators pay sites to help manage busy parts of the local network.

How much do batteries earn?

Income varies a lot month to month. According to market analysts Modo Energy, GB batteries averaged around £50,000 per MW across 2024. In September 2026 they averaged about £99,000 per MW (annualised), the best month since 2022, with about 69% of that from wholesale trading.

The trend over recent years is clear. Frequency response used to pay the most, but as more batteries joined, those prices fell. Trading now earns most of the money.

Revenue stacking and optimisers

Revenue stacking means earning from several of these markets, choosing the best each day.

Most battery owners don’t trade themselves. They use an optimiser (a specialist trading company) on one of three kinds of deal:

  • Merchant or profit share: the optimiser trades and takes a share of the income.
  • Floor: a guaranteed minimum income, with upside on top.
  • Toll: a fixed fee for the use of the battery, so the owner takes no market risk.

What it means for you

  • Landowners: you are usually paid rent, not a share of trading income, so your income doesn’t swing with the markets.
  • Developers and investors: the income mix affects how a site is valued and financed. A good grid connection and the right battery size matter most.
  • Businesses: an on-site battery can help you avoid peak prices and earn from local flexibility or schemes such as NESO’s Demand Flexibility Service. See what is a virtual power plant?

What we do

We develop battery and solar sites to ready-to-build and work with partners who trade and operate them. Battery storage development → · Partner with us →

Sources

Facts last checked 8 October 2026. Market figures change monthly. This is general information, not investment advice.