A solar array in Bishop’s Stortford lives two quite different lives. In June, PVGIS puts a south-facing 4 kWp array in the town at about 487 kWh for the month. In December the same roof makes about 137 kWh. The annual total, about 4,034 kWh, arrives very unevenly, and how you size panels and any battery depends on which part of the year you design for.
This guide uses PVGIS 5.3, the European Commission’s solar model, run for the town on 15 October 2026, alongside Ofgem’s typical consumption figure, to show what each season means for a household in Thorley, Hockerill or Windhill. For planning, generation and cost on your own roof, see our page on solar panels in Bishop’s Stortford.
The months side by side
The run uses the standard settings: 4 kWp, 35° tilt, due south, 14% system losses, building-mounted, on satellite data for 2005 to 2023.
| Month | PVGIS output, Bishop’s Stortford (kWh) | Average per day (our arithmetic) |
|---|---|---|
| June | about 487 | about 16.2 kWh |
| July | about 488 | about 15.7 kWh |
| December | about 137 | about 4.4 kWh |
| January | about 155 | about 5.0 kWh |
| Whole year | about 4,034 | about 11.1 kWh |
December makes about 28% of what June does, and January about 32% of July. The sunshine record tells the same story. The nearest Met Office station, Andrewsfield, publishes no sunshine average for 1991–2020, so the reference for the town is Writtle, near Chelmsford, which averaged about 1,644 hours a year: around 217 in July and around 52 in December, about four times as much in midsummer (our arithmetic). Shorter days, a low winter sun and duller skies all play a part.
Set against a household’s year
Ofgem’s typical domestic consumption value from 1 July 2026 is 2,500 kWh a year, about 6.8 kWh a day if it were spread evenly (our arithmetic). Real homes use more in winter than in summer, but even the flat average makes the point. On an average June day, the model array in Bishop’s Stortford makes more than twice that; on an average December day it makes about two-thirds of it. In June the question is what to do with the surplus. In December it is how little the roof covers.
Over the whole year, about 4,034 kWh against 2,500 looks generous. The monthly view is the more useful one, because electricity made in July cannot pay for a December evening without something to carry it.
Sizing the array: design for the year, not for December
Some people ask for enough panels to cover December. On the flat average, that would take roughly 6.2 kWp from the roof alone (6.8 ÷ 4.4 × 4 kWp, our arithmetic), which in June would make about 25 kWh a day, far more than the house can use, with the rest exported at a rate the supplier sets.
Roof space usually decides first anyway. The Energy Saving Trust’s typical system is around 4.5 kWp, about 12 panels over 20 to 30 m² of roof. In Bishop’s Stortford, where 32.6% of households live in detached houses and 28.8% in semis (Census 2021), many roofs can take that size. An east–west split, a lower pitch or a shaded slope changes every number in the table, so the survey re-runs the model for your own roof rather than borrowing the town figure.
Sizing a battery: design for the evening
A battery moves daytime output into the evening. In June a 4 kWp south-facing roof here averages about 16.2 kWh a day, enough for daytime use with plenty left to store. In December, about 4.4 kWh a day is likely to be used as it is made, leaving little or nothing for storage. So a battery sized to fill on summer days will rarely fill from the roof in midwinter, when its work is usually storing cheaper overnight electricity on a time-of-use tariff.
That is why we size storage from your evening use and tariff, not from June. The Energy Saving Trust says a typical home system might be 10 kWh and that there is no exact formula; our guide to what size home battery you need works through the method. For where a unit fits in a CM23 house, and the UK Power Networks paperwork, see our page on battery storage in Bishop’s Stortford.
Year to year, not only month to month
PVGIS gives the town’s annual figure a typical swing of about ±171 kWh between one year and the next, about 4% of the total (our arithmetic). A bright summer and a dull one differ, but by far less than June and December do. So judge an array over several years, and read little into one grey winter. Our guide to whether solar panels work on cloudy days explains why output falls in overcast weather but does not stop.
The planning calendar
One local factor affects the calendar rather than the output. Inside the Bishop’s Stortford Conservation Area, first designated in 1981, East Herts confirmed two Article 4 directions on 15 November 2017, and its leaflet says the direction for all properties brings the installation of renewable energy equipment on dwellings within the planning system, on all elevations. A house there needs planning permission for panels, whichever way the roof faces, so allow for the application in your plans. Once the panels are up, December and June look the same as anywhere else in town. Outside the boundary, the national permitted development rules apply. For neighbouring districts, see our solar panels in Hertfordshire hub.
Sources: PVGIS 5.3 (European Commission JRC), PVGIS-SARAH3 2005–2023, 4 kWp, 35°, due south, 14% losses, building-mounted, run 15 October 2026 (annual and monthly outputs; daily averages and ratios are our arithmetic); Met Office, Andrewsfield and Writtle location-specific long-term averages, 1991–2020; Ofgem, Typical Domestic Consumption Values (from 1 July 2026); Energy Saving Trust, Solar panels: costs, savings and benefits explained (updated 27 August 2026) and Battery storage (updated 19 August 2026); ONS, Towns and cities, characteristics of built-up areas, Census 2021 (table 5c); East Herts District Council, Bishop’s Stortford Conservation Area Article 4(1) Directions leaflet and Conservation Area Appraisal and Management Plan (December 2014).