GB Solar Smashes 15 GW: Four Records in 25 Days

A month Britain's grid will not forget

Four records. Twenty-five days. April 2026 has rewritten what British solar is capable of.

The sequence started on 6 April, when solar generation hit 14.1 GW at lunchtime — edging past the previous record of 14.0 GW set in July 2025. By the following morning it had already happened again: 14.4 GW on 7 April, back-to-back, confirmed by the National Energy System Operator (NESO). Notably, that second record fell on the same afternoon that Energy Secretary Ed Miliband announced planning approval for Springwell — set to become Britain's largest-ever solar farm.

Two weeks later, the story shifted from generation to the grid itself. On 22 April, between 15:30 and 16:00, zero-carbon sources covered 98.8% of GB electricity demand — a new national record, eclipsing the 97.7% high set just three weeks earlier on 1 April. Gas power stations sat almost entirely idle: their share fell to 1.2% of supply, an all-time low.

Then came the headline. At 11:30 on 23 April, solar crossed 15 GW for the first time in the history of GB grid data going back to 2009. By midday, the reading stood at 15,158 MW — 42% of the 36.4 GW total grid. Nearly one pound in every two of Britain's electricity at that moment was coming from the sun.

Why spring — not summer — breaks solar records

This surprises people every year. The explanation is consistent:

• Cool panels are more efficient. Solar cells lose roughly 0.4% of output for every 1°C above 25°C. A crisp April day at 14°C outperforms a warm August afternoon at 28°C, all else being equal.
• Days are nearly as long. By mid-April, daylight in southern England runs to around 14 hours — not far behind the 16.5 hours of the summer solstice, but with the efficiency advantage of cooler air.
• Spring air is cleaner. High-pressure systems typical of a settled April bring clear, dry conditions with minimal humidity, reducing the scattering of solar irradiance through the atmosphere.
• The fleet keeps growing. Every spring, more capacity has come online than the year before. The 15 GW record reflects not just a sunny day, but years of installation growth that only becomes visible in spring peaks.

The result is a pattern where April and May consistently produce the sharpest single-moment peaks — even when summer totals are higher overall.

What the zero-carbon record actually means

The 98.8% figure on 22 April is a grid-level story, not just a solar one. Wind led the way at 50.1% of supply during that half-hour period. Nuclear contributed 34.4%, and biomass added 9.8%. Solar's share in that specific window was 2.2% — smaller than its own generation records the day before and after, because the evening window caught solar on the way down.

The critical number is gas: 1.2%. For thirty minutes on a Wednesday afternoon, Britain's gas power stations were almost entirely offline while the lights stayed on, the factories kept running, and the grid stayed balanced. NESO chief operating officer Kayte O'Neill said at the time that a 100% zero-carbon sustained period is now within reach this summer.

What comes next

The floor is now 15.16 GW. With the summer solstice eight weeks away and installed capacity still growing, NESO's Summer 2026 Outlook flags that surplus renewable electricity periods will become more frequent — and that the record set on 23 April will likely fall before autumn.

For panel owners, the practical implication is simple: the biggest moments for the national grid are almost always the biggest moments for your roof. A record day for GB solar is a record day for you, too.