Metered, not modelled
Derby vs Swindon
Derby and Swindon roofs made much the same last year.
756 against 755 kWh per kWp at the median, from 245 and 119 real systems.
Where the two actually overlap
Both areas, grouped by what each system made. The medians differ, but the shapes sit largely on top of one another — a good Swindon roof beats a poor Derby one comfortably. Location moves the odds; it does not decide the outcome.
Derby: the middle half of 245 systems made 695–797 kWh per kWp. Swindon: the middle half of 119 systems made 666–847 kWh per kWp.
Both figures are what real systems metered last year, so the gap mixes sunlight with system age, roof direction and shading. It is the difference in what people actually got, not a difference in sunshine alone.
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Output figures from openclimatefix/uk_pv (Hugging Face, CC-BY-4.0), collected by Sheffield Solar. How we measure.
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