Put the same 4 kWp array on a roof in Edgware and on one in Romford, and over a year PVGIS says the Romford roof makes about 117 kWh more. Move either array from June to December and it loses about seven-tenths of its output. That contrast, small between boroughs and large between seasons, is the most useful thing to understand before sizing a battery anywhere in north London. Our hub on solar panels across north London covers each borough’s planning rules, grants and networks; this guide sticks to the calendar.
All the figures come from PVGIS 5.3, the European Commission’s solar model, run on 15 October 2026 for one town-centre point in each of six boroughs, with the settings we use across the site: 4 kWp facing due south at 35°, 14% system losses, on the 2005–2023 PVGIS-SARAH3 satellite record. They describe an unshaded roof in the best direction, so treat them as a ceiling for your house rather than a forecast.
Six boroughs, two months
| Town (borough) | June, kWh | December, kWh | December as share of June | Year, kWh |
|---|---|---|---|---|
| Edgware (Barnet) | 474 | 138 | 29% | 3,938 |
| Harrow (Harrow) | 477 | 140 | 29% | 3,965 |
| Wood Green (Haringey) | 475 | 142 | 30% | 3,956 |
| Enfield (Enfield) | 476 | 139 | 29% | 3,955 |
| Walthamstow (Waltham Forest) | 478 | 142 | 30% | 3,969 |
| Romford (Havering) | 489 | 143 | 29% | 4,055 |
Shares are our arithmetic on the PVGIS monthly figures.
Read across a row and the season dominates: June is roughly three and a half times December in every town. Read down a column and the boroughs barely differ. December runs from about 138 kWh in Edgware to about 143 kWh in Romford, a difference of 5 kWh over the whole month, or about 0.2 kWh a day. June’s spread, from 474 to 489 kWh, is wider but still small, and Romford, the furthest east, accounts for most of it.
The Met Office record agrees
PVGIS models sunshine from satellite data; the Met Office measures it on the ground, and the two tell the same story. Hampstead, the nearest sunshine station to most of these towns, averaged about 1,559 hours a year over 1991–2020, with about 194 in June and about 54 in December. Northwood, the nearest that records sunshine to Harrow, averaged about 1,556 hours, from about 209 in July to about 51 in December. Greenwich Observatory, the nearest to Romford, averaged about 1,526, with its dullest month January at about 44. The UK average on the same basis is about 1,403 hours. North London is sunnier than the country as a whole, and its winters are dim everywhere.
What the gap means day to day
Ofgem’s typical domestic consumption value from 1 July 2026 is 2,500 kWh a year, about 6.8 kWh a day. A June day in these six towns averages roughly 15.8 to 16.3 kWh from the 4 kWp array, so on those averages a house with the whole roof to itself makes about 9 to 9.5 kWh more than it uses (our arithmetic). Some of that is used in daylight anyway; what is left is the surplus a battery can carry into the evening, and without one it is exported.
December averages about 4.5 to 4.6 kWh a day across the six towns (our arithmetic), below the 6.8 kWh a typical household uses. Most of it is used as it is made, and a battery charged only from the roof will often start a December evening close to empty. No battery, however large, changes how little a north London roof makes in the shortest month, in Walthamstow or in Harrow.
Sizing to the evening, not to either month
The sensible size sits between the extremes. A battery big enough to soak up every June surplus would sit part-empty for much of the year, and no size fixes December. The question to answer is how much electricity your household uses between the panels going quiet and bedtime, and how much of that a typical spring, summer or early-autumn day’s surplus can cover.
The Energy Saving Trust says there is no exact formula. It describes a typical home system as perhaps 10 kWh, puts a 5 kWh system at around £4,600 and expects a battery to last about 10 to 12 years. Our guide to what size home battery you need shows how to read the evening figure from your own bills. For one borough worked through in more detail, see what a Finchley battery does in December and June.
Where the roof shrinks the numbers
The table assumes a whole 4 kWp roof, and north London’s housing often says otherwise. In Brent’s Wembley Park ward, 98.2% of households live in purpose-built flats, where any array is shared and the building owner’s permission comes first. At the other end, 41.2% of Havering’s households live in semi-detached houses, the second-highest share of London’s 33 local authorities, so a solar installation in Romford often has a full pitched roof to work with. A shared or partial roof shrinks both the June surplus and the December trickle, and the battery should shrink with them. Our town pages for solar panels in Edgware, Enfield solar panels and solar panels in Walthamstow carry each area’s housing and planning detail.
Winter options that are not solar
Because December output is so low across all six boroughs, some households look at charging a battery overnight on a time-of-use tariff and using it in the evening peak. That only pays where the gap between the cheap and standard rates is wide enough, and our guide to battery storage without solar panels sets out the arithmetic. One more winter point: a standard grid-tied battery shuts down in a power cut unless the system is designed with backup, so dark evenings alone are not a reason to buy one.
Getting a figure for your own roof
Everything above is modelled for an unshaded, due-south roof. Direction, pitch, shading and when your household uses power are what a survey measures, and they move the result far more than whether you live in Harrow or Havering. Residential solar and battery installations carry 0% VAT until 31 March 2027 and 5% from 1 April 2027. For storage in the borough with the highest yields on this list, see battery storage in Romford. If a battery would not earn its place on your house, we will say so.
Sources: PVGIS 5.3, European Commission Joint Research Centre (PVGIS-SARAH3 2005–2023; 4 kWp, 35°, due south, 14% losses; monthly and annual runs for Edgware, Harrow, Wood Green, Enfield, Walthamstow and Romford, 15 October 2026); Met Office, location-specific long-term averages 1991–2020 for Hampstead, Northwood and Greenwich Observatory; Ofgem, typical domestic consumption values from 1 July 2026; Energy Saving Trust, Battery storage (updated 19 August 2026); ONS Census 2021, TS044 Accommodation type via Nomis (Havering, all London local authorities, Wembley Park ward); UK Power Networks, Solar and storage: cost, time and what’s involved; HMRC, VAT Notice 708/6. Shares, daily figures and differences are our arithmetic.