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July 2026 was Great Britain's biggest solar month yet: what it means for a home buyer
NESO, the National Energy System Operator, publishes the half-hourly GB generation mix as open data. We downloaded the full file on 8 October 2026 and added up the solar column for every half hour of July 2026. This article uses only those sums. Everything below marked as ours is our arithmetic from NESO's published data, not a figure NESO itself has issued, and the dataset is at [the NESO Data Portal](https://www.neso.energy/data-portal/historic-generation-mix).
Our arithmetic from NESO's published data: solar supplied about 14.7% of GB generation in July 2026, roughly 3.3 TWh. Our share is solar divided by total generation in the same file, which includes imports. The nearest months were May (about 12.5%, 2.8 TWh) and June (about 12.3%, 2.8 TWh). July is the highest monthly share in the file for 2025 and 2026, so a record month stands up in the data we checked. We did not check the years before 2025, because solar was far smaller then.
Our arithmetic from NESO's published data: the best single day in July was 12 July, at about 19.1% of generation. The best day of the whole summer in our sums was 24 May, at about 19.7%. The highest half-hour of solar output in the file is 16.3 GW at noon on 23 April 2026. Press reports quote slightly lower figures for July (14.4% and 3.2 TWh) and for 12 July (18.8%). Ours come out a little higher. We can only say that the ranking and the rough size match; we have not worked out why the decimals differ, so treat any one figure as approximate.
Now the part that matters if you are thinking about panels on a Whitstable roof. The record is about the whole country's fleet of solar, not about what one house makes. Output follows the sun. In the same file, GB solar fell from about 3.3 TWh in July to about 0.5 TWh in January 2026. A home system behaves the same way: most of its yearly output lands between April and September, and July is among the best months, not a typical one. A yearly estimate is the number to use, not the summer headline.
A strong solar month also does not decide what you save. That depends on how much of the power you use yourself, because exported units earn the Smart Export Guarantee (SEG, the rate a supplier pays for power you send to the grid), which is usually well below what you pay to buy electricity. A house that is empty all day uses less of its midday output than one with someone at home, an electric car or a heat pump. A battery moves some midday power into the evening, at extra cost. We do not promise savings from a single month's weather.
What to do with this: ask for a yearly generation estimate for your roof, with its direction and shade, and ask how much of it the installer assumes you will use at home. Our cost guide shows modelled prices and paybacks for Whitstable homes, our guide to the Smart Export Guarantee explains export payments, and what size of solar and battery helps you match a system to your use. Installations are delivered with our MCS-certified installation partner.
Read the source: NESO Data Portal: Historic GB Generation Mix (our arithmetic from NESO's published data). Figures come from that page. Where we do our own sums we say so. The commentary is our own view, not advice.
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