​On 8 July 2025, solar generation in Great Britain hit 14 GW for the first time. For several hours that afternoon, solar was producing more electricity than gas, wind, and nuclear combined. Thats without including solar in the CfD scheme, which is set to bring 10 GW of solar online in the next few years.

That record output had a direct impact on battery trading. On 3 July, with solar peaking at 11.5 GW, the ME BESS GB index recorded £318/MW, 84% above the summer 2025 daily average. On 8 July, with solar at 14 GW, revenues fell to £155/MW, 10% below average. Solar is stretching intraday spreads on some days and compressing them on others, depending on how the output profile interacts with demand and wind.

Great Britain now has 21 GW of installed solar. The government wants 45 GW of total solar — rooftop and ground-mount combined — by 2030. That means more than doubling the fleet in five years, and the effects of CfD and non-subsidised solar on wholesale price formation, battery revenues, and capture rates will only intensify. Here is how we got here.

For further information on this topic, reach out to the author — zach@modoenergy.com

Key takeaways - solar buildout in three phases

• GB has approximately 21 GW of operational solar capacity. On high-solar days, wholesale price spreads are significantly affected.
• The fleet was built in three subsidy eras: FiT, RO, and CfD. Each responding to where solar sat on its cost curve.
• Solar deployed without FiT, RO, or CfD support — including domestic rooftop, commercial behind-the-meter, and merchant utility — now accounts for 8.6 GW.
• Utility-scale solar CAPEX has fallen 75% since 2010 — from £3,050/kW to £780/kW. In the UK, DESNZ puts current utility-scale (≥5 MW ground-mount) costs at £659/kWp, with a range of £526–788/kWp.
• The CfD pipeline alone contains over 12 GW from AR4–AR7a. Together with non-subsidy deployment, the total fleet could reach 41 GW by 2030 — just short of the 45 GW target.

Solar is already repricing the power market

At 21 GW, solar is significant enough to move prices, even during high demand. On clear summer days, solar output exceeds gas generation from late morning to mid-afternoon, suppressing midday wholesale prices and reshaping the intraday spread that batteries and flexible generators trade around.

The impact varies day to day. High solar output can widen the gap between midday lows and evening peaks, creating trading opportunities. Or, if sustained through the afternoon, it can flatten the curve and compress spreads. Both effects are becoming more pronounced as the fleet grows.

For solar developers, each additional gigawatt suppresses the wholesale price at the exact hours when solar generates. Solar capture rates are projected to fall from 89% to 68% over the next decade, similar declines have occurred in Germany and Spain, countries with significant solar buildout.

That cannibalisation is one reason the government brought solar back into the CfD scheme — merchant revenues alone were not sufficient to sustain the build rate that net zero requires.

Solar was built in three distinct phases

Great Britain's 21 GW solar fleet was assembled in three eras, each a response to where the technology sat on its cost curve.

The FiT era (2010–2019)

Launched at 41.3p/kWh for small rooftop systems — over eight times today's wholesale price — because that was what it took when solar cost £3,050/kW to install. Over nine years it drove 5.1 GW across 860,000 mostly residential rooftops. A 64% tariff cut in January 2016 halved annual additions overnight, and the scheme closed in 2019 at 3.8p/kWh.

The Renewable Obligation era (2013–2017)

Ran in parallel, offering tradeable Renewables Obligation Certificates (ROCs) — each worth around £45–50. With solar receiving 1.2–2.0 ROCs per MWh, total subsidy value hit £58–90/MWh.

This drove a concentrated burst of utility-scale solar — 5.7 GW across 878 stations. Deployment followed a distinctive quarterly pattern: projects needed accreditation by 31 March each year, creating enormous Q1 spikes. Q1 2015 alone saw 2.3 GW come online.

The lull (2019–2022)

In 2020, both schemes had closed. The government excluded solar from its CfD allocation rounds, deeming it "an established technology" that could survive on merchant revenues. It was right about the technology. It was wrong about the pace. Annual additions collapsed to 300–400 MW — a fraction of the 4–5 GW per year that net zero demanded.

Two things changed the trajectory. The energy price crisis of 2022 made domestic solar economics irresistible: at retail prices of 25–30p/kWh, a rooftop system paid for itself in 5–7 years. Domestic installations spiked and have stayed above 20,000 per month since. And the government brought solar back into the CfD from AR4 in 2022.

The CfD return (2022–present)

Solar has been the most prolific technology by project count in every allocation round since AR4. AR7a, announced in February 2026, awarded 4.9 GW — the largest solar procurement in UK history — at a strike price of £65/MWh, over 10% cheaper than AR6. Only 546 MW of CfD solar was operational by the end of 2025, but the pipeline is vast: over 12 GW awarded across AR4–AR7a.

Alongside the subsidy pipeline, unsubsidised solar has boomed. Domestic rooftop, commercial behind-the-meter, and non-subsidised utility — grew from 2.8 GW at the end of 2022 to 8.6 GW at the end of 2025.

As build costs have reduced, the case for solar backed by PPAs has improved, while rooftop solar has become more accessible to the general public.

The RO (5.7 GW) and non-subsidised (8.6 GW) categories make up two-thirds of today's portfolio. FiT accounts for 5.1 GW across 860,000 installations. CfD currently accounts for a small share, but with 10 GW in the pipeline, it will become the fleet's largest category.

Buildout is below CP30 pace - but CfD pipeline is coming

2025 added 2.6 GW — the strongest year since 2016. But the Clean Power 2030 plan requires 4.7 GW per year for five years. 2025's pace is 55% of what is needed.

Two forces are driving the next wave. The CfD pipeline — over 12 GW awarded across AR4–AR7a — is the most certain component. Alongside it, continued capex reductions are strengthening the merchant case, particularly for solar co-located with battery storage.

Together, CfD and merchant deployment suggest the fleet reaches roughly 41 GW by 2030 — a near-doubling from today, but short of the 45 GW target. Grid connection timelines are the binding constraint. The next five years should deliver more solar than the previous fifteen combined.