Will a Home Battery Fill Up in Winter? Barnsley Solar Output, Month by Month

ElectriFusion Solutions · 16 September 2026

A common question about home batteries is simple: how much of the day's solar will the battery actually catch? The answer changes so much through the year that a single annual figure is close to useless. Here is the whole year for a south-facing roof in Barnsley, taken from the European Commission's PVGIS model.

A 4.85 kW array in Barnsley, every month

PVGIS 5.2 (EU Joint Research Centre), Barnsley town-centre coordinates, south-facing at 35°, 14% losses. Annual total: 958 kWh per kW of panels, about 4,650 kWh for this array.

What that means for the battery

April to August is when the roof does the heavy lifting, with the array averaging 17 to 19 kWh a day. On an average day in those months that leaves enough to fill a 10 kWh battery if the house uses less than about 7 kWh while the sun is up.

March, September and October are shoulder months: 9 to 15 kWh a day. On an average day a 5 kWh battery fills if the house uses less than about 8 kWh while the sun is up in March and September, and less than about 4.5 kWh in October; a larger one needs a brighter day.

November to February the array averages 5 to 9 kWh a day, and in December and January barely 5. Even the best of those averages is less than a 10 kWh battery holds before the house uses any of it, so a battery sized for summer cannot fill from solar on an average winter day unless something else charges it.

That something else is the grid

A time-of-use tariff lets the battery fill overnight when electricity is cheapest. On Octopus's Flux tariff for homes with solar and a battery, the published rates for the Yorkshire region on 16 September 2026 were: import cost 14.64p per kWh between 02:00 and 05:00 against 34.16p between 16:00 and 19:00 (import rates including VAT at 5%, which comes off household electricity on 1 October 2026). A battery supplied and installed in a home by the installer is zero-rated for VAT until 31 March 2027, including one that only charges from the grid.

Just do not count the battery twice. Filled from the grid overnight, a battery is already full when the morning's solar surplus arrives, so on any one day the two uses compete for the same capacity. Model solar storage and grid charging separately, month by month, rather than adding the two together.

Barnsley has already tried this

Adding batteries to homes that already had panels is not new locally. Energise Barnsley, a community energy society, ran a Smart Solar project from May 2021 to September 2023 that did exactly that. The month-by-month figures above are the reason such projects look closely at when a battery can actually fill.

So what size?

If you want a battery mainly to store summer solar from a south-facing array of around 4.85 kW, the figures above point to 5 to 10 kWh. Go larger if you have an electric car, high evening use, or you intend to charge from the grid in winter. For how we size, connect and quote a battery locally, see our page on battery storage in Barnsley.

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