Twelve numbers explain most of what a battery can and cannot do on a Barnet roof. They are the monthly outputs PVGIS 5.3, the European Commission’s solar model, gives for a 4 kWp array facing due south at 35° in High Barnet, with 14% system losses, averaged over its 2005–2023 satellite record. Read in order, they show which months a battery fills from the roof, which months it half-fills and which months it barely notices the panels at all. Our page on battery storage in Barnet covers where a unit fits and how UK Power Networks is told; this guide is about the calendar.
The annual total for that point is about 3,959 kWh, the same figure on our Barnet solar page. It is a best case for an unshaded roof. A gable next door, a tall tree on a green-belt edge or an east-facing slope all pull it down, so treat everything below as a shape rather than a promise.
The Barnet year in twelve figures
| Month | PVGIS output, kWh | Per day, kWh (our arithmetic) |
|---|---|---|
| January | 157 | 5.1 |
| February | 208 | 7.4 |
| March | 337 | 10.9 |
| April | 442 | 14.7 |
| May | 466 | 15.0 |
| June | 477 | 15.9 |
| July | 483 | 15.6 |
| August | 433 | 14.0 |
| September | 371 | 12.4 |
| October | 263 | 8.5 |
| November | 184 | 6.1 |
| December | 139 | 4.5 |
For scale, Ofgem’s typical domestic consumption value from 1 July 2026 is 2,500 kWh a year, about 6.8 kWh a day. The Met Office station at Hampstead, the nearest to Barnet with a sunshine record, tells the same story in hours: about 200 in July, about 54 in December and 1,559 across an average year (1991–2020).
Season one: April to September, the battery’s working months
These six months make about 2,672 kWh, roughly 67% of the year’s output (our arithmetic). On an average day the roof makes twice what a typical household uses across a whole day, and much of that arrives while the house is quiet. This is when a battery earns its keep: it takes the afternoon surplus that would otherwise be exported and hands it back after dark. In these months the limit is usually the battery’s size or the evening’s demand, not the roof.
Season two: March and October, the months that decide the size
The shoulder months are where sizing decisions are really made. The Barnet array averages roughly 10.9 kWh a day in March and 8.5 in October. Some of that is used in daylight, so the surplus left for a battery is smaller and less reliable than in summer. A battery that still fills on a typical March or October day will fill through the whole summer too. One sized to swallow every June surplus will sit part-empty for these months and for the four that follow. The Energy Saving Trust says there is no exact formula and describes a typical home system as perhaps 10 kWh; our guide to what size home battery you need shows how to read your bills for the evening figure.
Season three: November to February, little to store
November, December, January and February together make about 688 kWh, about 17% of the year (our arithmetic). In three of those months, November, December and January, the array averages less per day than Ofgem’s typical household uses, and in December the gap is widest at about 4.5 kWh a day against 6.8. A Barnet house in midwinter usually uses what the roof makes as it is made. No battery, however large, changes how little a north London roof produces in the shortest days.
What a battery can still do in winter is store electricity bought at a cheaper overnight rate and use it in the evening peak, if your tariff has a wide enough gap between the two. That is a tariff decision rather than a solar one, and our guide to battery storage without solar panels sets out the sums honestly.
How Barnet’s houses shift the calendar
The table assumes a whole 4 kWp roof. In High Barnet ward, 23.7% of households live in detached houses, 24.7% in semis and 20.2% in terraces, and 67.6% own their home, so many households do control a roof that size. In Barnet Vale, 37.2% live in purpose-built flats, where an array is often shared or smaller and the freeholder decides what can be fitted. Halve the array and every row in the table halves with it: the working months shrink and the shoulder months start to look like winter.
Heat is the other seasonal factor. In the Chipping Barnet constituency the median detached and semi-detached house both score 62 on the EPC scale, band D, against 74 for flats (ONS, records to March 2025). A battery does nothing for heat loss, and in a band D house insulation often belongs in the same conversation.
Planning rarely changes the sums. Wood Street and Monken Hadley are among the borough’s 16 conservation areas and both carry Article 4 directions, but Barnet’s records do not list the solar class among the rights those directions remove; a battery fitted indoors or on a rear wall stays out of view either way.
Winter, power cuts and the honest limit
Dark evenings are not, on their own, a reason to buy a battery. Barnet’s town centre is in UK Power Networks’ Eastern Power Networks area, and a standard grid-tied battery shuts down in a power cut, however full it is, so nothing feeds lines engineers may be working on. Backup has to be designed in with a suitable inverter and a way to isolate the house, and it is priced separately.
If panels are still undecided, our page on solar panels in Barnet covers the roof side, and the North London solar panels hub covers the wider area. Residential batteries carry 0% VAT until 31 March 2027 and 5% from 1 April 2027. If a battery would not earn its place across your year, we will tell you.
Sources: PVGIS 5.3, European Commission Joint Research Centre (PVGIS-SARAH3 2005–2023; 4 kWp, 35°, due south, 14% losses, building-mounted; High Barnet point used for our Barnet pages, run 15 October 2026, monthly series re-run 18 October 2026); Ofgem, typical domestic consumption values from 1 July 2026; Met Office, Hampstead location-specific long-term averages 1991–2020; Energy Saving Trust, Battery storage (updated 19 August 2026); ONS Census 2021, TS044 and TS054, High Barnet and Barnet Vale wards, via Nomis; ONS, Energy efficiency of housing in England and Wales, EPC records to March 2025, tables 4a and 4b; planning.data.gov.uk, conservation-area and article-4-direction-area datasets, London Borough of Barnet; UK Power Networks, licence boundaries open data; HMRC, VAT Notice 708/6. Per-day figures, seasonal totals and percentages are our arithmetic on the PVGIS and Ofgem figures.