Quick answer
A battery holds daytime surplus for later, so it helps most from March to September, when a 3 kWp south roof in Winsford averages eight kWh a day or more. Combined panels and storage above 3.68 kW per phase need G99 approval. VAT on installed batteries is zero until 31 March 2027. Keep it dry and off floodable floors.
What a battery does
Without storage, any electricity the house is not using at the moment the panels make it goes to the grid. A battery catches some of that surplus and releases it later, typically in the evening, when the panels have stopped and the household is cooking, washing and watching television. It raises the share of the roof’s output used at home and lowers the share exported. It does not make the panels produce any more.
Batteries are described by their capacity in kWh, of which only part is usable, and by the rate at which they can charge and discharge in kW. Some energy is lost in each cycle of charging and discharging. They wear gradually, so a warranty normally promises a minimum share of the original capacity after a stated number of years or cycles. How a battery fits with the rest of the system is explained alongside self-use on export and self-use.
When there is surplus to store in Winsford
A battery only helps when there is something to put in it. Using the PVGIS figures for Winsford, a 3 kWp south-facing roof at 35° makes about 11.7 kWh on an average June day and about 2.8 kWh on an average December day (PVGIS 5.3). From March to September the average day brings eight kWh or more, often well beyond what a house uses while the sun is up. From November to January the roof makes little enough that the house uses nearly all of it as it comes, and the battery has little to do unless it is charged from the grid.
So in Winsford a battery earns most of its keep across the brighter half of the year. Any proposal that assumes it will be filled by the panels every day in midwinter should be questioned. The monthly pattern for every direction is on what panels make in Winsford.
Sizing, in general terms
Two numbers bound the sensible size. One is the household’s evening and overnight use, the electricity it would draw from the battery after sunset. The other is the typical summer surplus, what is left over after daytime use. A battery much larger than the evening use will rarely empty; one much larger than the surplus will rarely fill. Ask the firm what assumptions it has made about both, and whether they come from your own meter readings or from a standard profile.
Households with an electric car, or plans for one, have more evening demand and may justify more storage. Households out all day and in bed early may need very little. Size on the spring, summer and autumn months, not on December.
Now or later
A battery can go in with the panels or be added afterwards. Fitting both at once means one visit, one set of paperwork and, often, a single hybrid inverter that handles both panels and storage. Adding a battery later is also common; it may connect through its own inverter on the house’s alternating-current side, which leaves the existing panels untouched. If you are unsure, ask for a quote for panels alone that keeps the later option open, and ask what that later addition would involve.
The grid rules for storage
The network operator counts storage as generation, because a battery can feed electricity into the grid. The usual threshold is 16 A per phase, which on a normal single-phase home supply is 3.68 kW. If the combined inverter capacity of panels and battery is within that, the firm can install first and notify the operator within 28 days under G98. If the combination goes over, the firm must apply under G99 and wait for approval before connecting. Some systems use export limitation so that the most they can send to the grid stays within a figure the operator has agreed; the application should say so.
The Energy Networks Association’s postcode search shows which operator covers a Winsford address. Grid connection sets out both routes in more detail.
VAT
Batteries installed in homes carry 0% VAT until 31 March 2027, with 5% applying from April 2027, under HMRC’s Notice 708/6. The rate covers the installed job, and the firm applies it on the invoice; nobody has to apply for it. If installation might finish close to the changeover, ask which rate the price assumes. The wider picture of costs is on solar costs in Winsford.
Where the battery goes
Placement matters more for a battery than for any other part of the system. A good position is dry, ventilated, within the manufacturer’s temperature range, reachable for inspection, and away from the only route out of the house. Garages, utility rooms and outside walls are common choices; under-stairs cupboards on an escape route and cramped lofts are often not.
Winsford adds one local consideration. The council’s planning paper notes flood-risk areas associated with the Bottom Flash and the course of the River Weaver through the town (Places background paper, 2024). For a home near either, a battery at floor level in a garage, outbuilding or low utility room is worth avoiding. Ask whether the unit can be wall-mounted well above the floor, whether the inverter and isolators can go higher too, and how the firm has allowed for water. If a space has taken water before, say so at the survey. The salt town and solar has more on the river and the flashes.
Batteries in rented homes and flats
In a rented home a battery is the landlord’s equipment once fitted, and needs the landlord’s written agreement like any other alteration. In a block of flats the building owner’s responsibilities for fire safety in shared buildings can make storage inside individual flats harder to agree, and the owner may prefer a shared arrangement. Who decides about solar sets out whose agreement is needed.
Living with a battery
Once fitted, a battery mostly runs itself, but it is worth knowing how to read it. The monitoring app or display shows its state of charge, how much it took in from the panels and how much it gave back to the house. Watching that for a few weeks in spring and again in autumn shows whether the size is right: a battery that is full by mid-morning and still part-full at dawn is larger than the household needs, while one that empties by early evening is working hard. Firmware updates, if the system takes them, change how it behaves, so ask the firm who manages them. At the end of its working life a battery has to be removed by someone competent and recycled, not put out with household waste.
Questions for a battery quote
- What is the usable capacity in kWh, and the charge and discharge rate in kW?
- What does the warranty promise, for how long, and what share of capacity is it measured against?
- Where exactly will it go, and why there?
- Does it provide backup in a power cut, and if so for which circuits?
- Will the system go through G98 or G99, and is export limitation proposed?
- What assumptions about daytime and evening use lie behind the recommended size?
Run the usual checks on the firm, set out in choosing an installer, and send any question about your own home through the question form.