When there is spare power
A battery only earns its place if the panels sometimes make more than the house is using. PVGIS gives month-by-month output at the best angle for the city centre (PVGIS 5.3), and Ofgem puts typical household use at 2,500 kWh a year (Ofgem), which averages 6.8 kWh a day. For a 3.5 kW system:
| Month | Made a day | Against use |
|---|---|---|
| January | 4.0 kWh | 2.9 kWh short |
| February | 6.4 kWh | 0.5 kWh short |
| March | 9.5 kWh | 2.6 kWh spare |
| April | 12.4 kWh | 5.5 kWh spare |
| May | 13.0 kWh | 6.1 kWh spare |
| June | 12.7 kWh | 5.9 kWh spare |
| July | 12.8 kWh | 5.9 kWh spare |
| August | 11.9 kWh | 5.0 kWh spare |
| September | 10.0 kWh | 3.2 kWh spare |
| October | 6.7 kWh | 0.2 kWh short |
| November | 4.8 kWh | 2.1 kWh short |
| December | 3.5 kWh | 3.3 kWh short |
From spring to early autumn the panels outrun the household's average day, and most of that surplus comes around midday, when a working household is out. A battery charged then can run the evening. Through the winter months the panels fall short of the day's use, so a battery fed only by them has little to store. Real days swing with the weather and with how you live; a household at home in the day uses more of its own solar without a battery.
Two months show the range. In July an average day leaves about 5.9 kWh spare from a 3.5 kW system in the city centre; in December the same system falls about 3.3 kWh short of an average day's use (our arithmetic from PVGIS and Ofgem). A battery of around the July figure fills on a typical summer day and sits largely idle in winter unless it is also charged from the grid overnight, which is a question about your electricity tariff rather than your panels.
What it costs
DESNZ records what households paid for batteries added to existing homes. In 2025/26 the median was £1,300 per kWh for batteries under 6 kWh, £890 from 6 to 11 kWh and £630 from 11 to 30 kWh (DESNZ). At those medians, by our arithmetic, a 5 kWh battery comes to about £6,500, a 9.5 kWh one about £8,450 and a 13.5 kWh one about £8,500.
Batteries installed in homes are zero-rated for VAT until 31 March 2027, the same as panels (HMRC). Bradford Council has delivered battery storage alongside solar under the Warm Homes: Local Grant for eligible households: homes at EPC D to G where the household qualifies on postcode, benefits or income under £36,000 (Bradford Council). For the panels' side of a combined quote, see what solar costs.
Batteries in the council's grant installs
Bradford Council says it has delivered solar PV and battery storage together under the Warm Homes: Local Grant, for homes at EPC D to G where the household qualifies on income, benefits or postcode (Bradford Council). If your battery came that way, keep its paperwork with the panels' MCS certificate and note who to contact about a fault. The council has also warned that some offers made after these installations are not connected to it or its partners, and that the installation commits nobody to further work. If someone later offers to replace or add to a grant-funded battery, check with the council first. See help with the cost for the scheme's rules and choosing an installer for the checks on any firm.
Northern Powergrid
Northern Powergrid runs the network in the district. A battery counts towards the connection limit along with the panels: within 16 A per phase (3.68 kW on a single-phase supply) the installer connects and then notifies Northern Powergrid; beyond it, an application is needed first (Northern Powergrid; small-scale generation). Some installers limit export instead to stay inside the smaller route. The quote should say which. How the connection works
Where it goes
PAS 63100, the BSI code of practice for battery storage in homes, governs where one can go and excludes places such as escape routes and bedrooms (BSI). With 33% of households in a terrace (Census 2021), many Bradford homes have no garage, which narrows the choice; an outbuilding or an outside wall may suit, but only where the code allows. Ask the installer to show the spot on the survey, say why it meets the code, and how the cable gets there from the inverter. In a stone terrace that cable route can mean drilling through thick walls, which belongs on the quote too.
What a battery quote should say
- The make, model and usable capacity in kWh, and the warranty in years and cycles.
- Whether it couples to the existing inverter or needs a new one, and whether that is priced in.
- Where it will be fitted, and how that meets PAS 63100.
- Whether the system now needs a Northern Powergrid application or export limiting.
- The battery on its own line, so the panels can still be compared per kW.
- Whether it can keep some circuits running in a power cut, and whether that needs extra equipment on the quote.
- How the battery will be reached for servicing once it is in place, especially if it goes in an outbuilding or behind a stud wall.
For the checks on the firm itself, see choosing an installer.