| Month | 4 kWp array, Wokingham (PVGIS) | Per day (our arithmetic) |
|---|---|---|
| December | about 137 kWh | about 4.4 kWh |
| January | about 158 kWh | about 5.1 kWh |
| June | about 479 kWh | about 16.0 kWh |
| July | about 483 kWh | about 15.6 kWh |
| Whole year | about 3,964 kWh | about 10.9 kWh |
That table is the whole case for how to size a battery in Wokingham, and most sales pitches skip it. The figures come from the European Commission’s PVGIS 5.3 tool, run for Wokingham town centre with a 4 kWp array facing due south at 35°, 14% system losses and building-mounted, on satellite data for 2005 to 2023. A December day’s output is roughly 29% of a June day’s (our arithmetic). Our Wokingham battery storage guide covers the rest: where a unit goes, the grid and what a battery does in a power cut. This guide stays with the seasons.
June: more than the house can use
On a typical June day the array makes about 16 kWh. Ofgem’s typical household uses 2,500 kWh a year, about 6.8 kWh a day if spread evenly (our arithmetic). The real profile is not even, and most of the use is not at midday. Without a battery, much of a June day’s generation is exported while the house is empty, and then bought back in the evening.
This is where a battery earns its keep. It stores some of the midday surplus and releases it after dark. A battery that covers your evenings and overnight use catches most of the useful surplus. Anything larger mostly stores energy that would otherwise be exported.
December: little left to store
On a December day the same array makes about 4.4 kWh, and January is a little better at about 5.1 kWh. Most of that is used as it arrives, by the fridge, the router and whatever else is on during daylight. Little is left over for the battery. No size of battery changes this. A bigger battery does not make more sunlight. It just sits partly empty from November to February.
This is why we do not size a battery for winter self-sufficiency, and why no honest quote should promise it. In winter, a battery’s job is usually different. On a time-of-use tariff it can be charged from the grid when electricity is cheaper and used at the evening peak. Whether that pays depends on the tariff you are on, so judge it against your own bills.
So what size?
The Energy Saving Trust says there is no exact formula. It suggests a typical home system might be 10 kWh and puts a 5 kWh system at around £4,600 (updated 19 August 2026). A practical way to size:
- Look at what you use between about 4pm and bedtime on an ordinary weekday. Smart-meter data shows this.
- Compare it with the June surplus. On a 4 kWp array the surplus is usually well above what an evening needs, so evening use is the limit, not the roof.
- Treat December as the time-of-use case, not the solar case.
Our guide to what size home battery you need works through that step by step. If you are wondering how far grey days drag the figures down, our guide to solar on cloudy days explains why output falls but does not stop.
Wokingham’s houses make the summer gap bigger
Wokingham borough’s housing is unusually spacious. At the 2021 Census, 42.7% of its 69,165 households lived in detached homes and 29.2% in semi-detached homes, and 76.0% were owner-occupied. Wide roofs invite larger arrays, and a larger array makes the seasonal gap bigger in absolute terms. Doubling a 4 kWp array to 8 kWp would roughly double both lines of the table (our arithmetic): about 32 kWh on a June day, but still under 9 kWh on a December day. The extra panels mostly add summer surplus, which raises the value of a battery in summer and does nothing for it in winter.
The borough’s population grew 15.0% between 2011 and 2021, and much of that growth is in new homes. On a newer estate, the first practical question is whether the developer has already fitted panels. If so, the table above still applies, scaled to whatever is on the roof.
The grid side, briefly
Wokingham’s town centre sits on SSEN Distribution’s Southern Electric Power Distribution network, about 14.8 km from the nearest other licence area. A system whose inverters, including the battery’s, total up to 16 A (3.68 kW) per phase is notified under G98. Above that, a G99 approval is needed before work starts. A standard grid-tied battery shuts down in a power cut unless it was designed and installed for backup.
For the panel side of the decision, our solar panels Wokingham page covers the borough’s conservation areas and its Barkham solar farm. For the wider county, see solar panels in Berkshire.
Sources: PVGIS 5.3 (European Commission Joint Research Centre), PVGIS-SARAH3 2005–2023, 4 kWp, 35°, due south, 14% losses, run 15 October 2026; Ofgem, typical domestic consumption values (from 1 July 2026); Energy Saving Trust, Battery storage (updated 19 August 2026); ONS Census 2021, TS044 and TS054 (Wokingham) and How life has changed in Wokingham; NESO, GB DNO licence area boundaries; SSEN, Who we are; ENA EREC G98 Issue 2.