The University of Reading has been measuring sunshine at its Atmospheric Observatory at Whiteknights since 1956, and the 1991–2020 average comes out at 1,567 hours a year. That annual figure hides the number that matters most for a battery: how unevenly the sunshine falls between a Reading June and a Reading December. A battery that suits one month can sit nearly empty in the other.
This guide puts numbers on that gap for a Reading roof and explains what it means for choosing a battery size. If you want the wider local picture of battery storage in Reading, including the network and housing data, our main page covers it. Here we stick to the calendar.
Reading’s June and December in kilowatt-hours
PVGIS 5.3, the European Commission’s solar calculator, estimates that a 4 kWp array facing due south at 35° in Reading produces about 4,049 kWh a year, on its satellite record for 2005 to 2023. Split by month, the year is lopsided:
- June: about 495 kWh
- July: about 499 kWh
- January: about 155 kWh
- December: about 140 kWh
On our arithmetic, December produces about 28% of what June does, and January about 31% of July. These are figures for an unshaded, due-south roof; an east- or west-facing slope in Caversham or Tilehurst will produce less, and shading changes the answer more than the town does.
What an average day looks like
Dividing by the days in each month, the same Reading array averages roughly 16.5 kWh a day in June and 16.1 kWh in July, but only about 5.0 kWh a day in January and 4.5 kWh in December. Ofgem’s typical domestic consumption value from 1 July 2026 is 2,500 kWh a year, about 6.8 kWh a day.
Put those side by side and the two seasons tell different stories. In a Reading June, even a household that used its whole daily average while the sun was up would have about 10 kWh left over on an average day. In December the array’s whole output is less than that household’s daily use, so almost every unit is used in the house as it is made, and there is little or nothing left to store. Real days swing either side of these averages, which is why PVGIS is a guide, not a promise.
Why the battery is sized for the evening, not for winter
A battery stores what you have made and not yet used. In a Reading summer that surplus is large, and the battery’s job is to carry it from the afternoon into the evening, when the household is home, cooking and running appliances. In winter there is little surplus, and no reasonable battery changes that; a home cannot store June’s sunshine for December.
So the size that makes sense is the size of your summer evening use, not a figure chosen to get through January. The Energy Saving Trust says there is no exact formula and that a typical home system might be 10 kWh, with a 5 kWh system costing around £4,600. For many Reading households the right figure sits somewhere around those two, set by meter readings rather than by the box size. Our guide to what size home battery you need walks through that from your own usage.
What a battery does in a Reading winter
In December and January the battery’s role changes. With little solar surplus to store, it can be charged from the grid overnight on a time-of-use tariff and used in the evening when the unit price is higher. Whether that pays depends entirely on the gap between your two rates, so it is a tariff question, not a solar one. If the winter months are your main reason for wanting a battery, our guide on battery storage without solar panels sets out when grid charging stacks up and when it does not.
The Reading-specific checks
Three local points sit alongside the seasonal maths. First, ownership: at the 2021 Census, 50.4% of Reading households were owner-occupiers and 31.9% rented privately, so for nearly a third of homes a landlord decides whether a battery goes in. Second, the housing runs from Victorian terraces in the town’s 15 conservation areas to new homes at Green Park Village, and where the battery physically goes differs between them. Third, the network: Reading is on SSEN’s Southern Electric Power Distribution network, whose registered office is at No.1 Forbury Place in the town, and your installer notifies it under G98 for systems up to 16 A per phase (3.68 kW) or through a G99 application, approved before work starts, for anything larger.
A sizing checklist for a Reading home
- Read your meter in the late afternoon and at bedtime for a week in a Reading June, when a south-facing 4 kWp array averages about 16.5 kWh a day; the evening difference is roughly what a battery can usefully cover.
- Repeat it for a week in December, when the same array averages about 4.5 kWh a day; that tells you whether grid charging on a cheaper tariff is worth costing.
- If you are among the 31.9% of Reading households renting privately, put the landlord conversation first.
- Check where the unit can go near your consumer unit, which differs between a Victorian terrace in one of Reading’s 15 conservation areas and a new home at Green Park Village, before choosing a size.
Our page on solar panels in Reading covers the roof itself, and our Berkshire solar guide takes the county view.
Sources: PVGIS 5.3 (European Commission Joint Research Centre), PVGIS-SARAH3 2005–2023, 4 kWp, 35°, due south, 14% losses, building-mounted, run 15 October 2026; University of Reading, Department of Meteorology, Atmospheric Observatory; Ofgem, Typical Domestic Consumption Values (from 1 July 2026); Energy Saving Trust, Battery storage (updated 19 August 2026); ONS, How life has changed in Reading: Census 2021; Reading Borough Council, Conservation areas and listed buildings; SSEN, Who we are; Energy Networks Association EREC G98 Issue 2 (10 March 2025).