The short version
A battery helps most where plenty of daytime solar would otherwise be exported and the household uses more power in the evening. It can push a system past the 3.68 kW single-phase limit, which means a G99 application before connection. Installed batteries carry 0% VAT until 31 March 2027, then 5% from 1 April 2027.
What a battery does and does not do
A home battery stores electricity your panels make when the house does not need it, and releases it later when the panels have stopped. It does not increase what the roof produces, and a little energy is lost every time it charges and discharges. Its value comes from moving units you would have exported, at the export rate, into hours when you would otherwise buy them at the import rate. In other words, a battery is a tool for raising self-use, which is explained in export and self-use.
Many batteries can also be charged from the grid. On a tariff with a cheaper overnight rate, a battery can fill up at night and run the house through the morning or the evening. That use has nothing to do with solar and works in any season, which matters in a Northwich winter when the panels have little spare to give.
When a battery tends to help
- The house is empty during the day. If everyone is out at work or school, much of a summer day’s output leaves the property. A battery can keep some of it for the evening.
- Evening use is heavy. Cooking, washing and screens after dark line up well with stored solar.
- The array is large for the household. A big array produces more spare in summer than a modest one.
- A time-of-use tariff is available. Cheap overnight charging gives the battery a job in winter.
- Heating or transport runs on electricity. Households that heat electrically or charge a car at home have more use for stored units.
When it helps less
- Someone is at home through the day and already uses most of the output.
- The array is small, so there is little surplus to store.
- The household uses little electricity in the evening.
- There is nowhere suitable to put the unit. The location has to satisfy both the manufacturer’s instructions and the installer’s assessment.
The Northwich seasons and a battery
The size of the surplus swings hugely through the year. Using PVGIS 5.3 figures for a due-south 35° roof near Northwich, a 4 kWp array averages about 15.5 kWh a day in June but only about 3.5 kWh a day in December. In June, a household that is out all day may send a good part of that to the grid. In December there is rarely anything left once the fridge, the lights and the boiler controls have taken their share. A battery sized to capture summer surplus will sit partly empty from late autumn to early spring unless it is also charged from the grid.
That is not an argument against batteries, only a reason to think about how one would earn its keep in each season. Ask the installer to show the expected surplus month by month rather than a single yearly figure. The full monthly pattern for the town is on output on a Northwich roof.
Electric heating in Leftwich and nearby wards
The 2021 Census asked households what their central heating ran on. In the Leftwich ward, 10.9% of households reported electric-only heating, the highest share of the seven wards in and around Northwich covered by this guide (Census 2021).
| Ward | Households | Electric only |
|---|---|---|
| Northwich Leftwich | 2,279 | 10.9% |
| Northwich Winnington & Castle | 4,065 | 5.8% |
| Hartford & Greenbank | 3,814 | 5.7% |
| Northwich Witton | 2,336 | 5.5% |
| Shakerley | 2,182 | 3.2% |
| Rudheath | 2,484 | 2.8% |
| Davenham, Moulton & Kingsmead | 4,571 | 2.8% |
For a home heated by electricity, a battery’s winter work is mostly about the grid rather than the roof. Charging overnight on a cheaper rate and drawing down through the day can make heating hours cost less, depending on the tariff. Solar helps such homes most in spring and autumn, when heating is still needed but the panels are producing well. Leftwich also has a high share of flats and social renting, so many households there will need a landlord’s or building owner’s agreement before anything is fitted; see renters and flats.
Grid connection: when a battery triggers G99
Every generating system connected to the local network has to be notified to, or approved by, the distribution network operator. On a single-phase supply, a set-up with combined inverter output of up to 3.68 kW, which is 16 amps per phase, goes through the simpler G98 route: the installer notifies the operator within 28 days. Above that, the installer applies under G99 and waits for approval before connecting. The rules appear in network operators’ connection guidance (SP Energy Networks’ version is one example), and the ENA postcode search tells you which operator serves your own address.
The key point for battery buyers is that the limit counts inverter output, not panel size. A battery either brings an inverter of its own or shares a hybrid inverter with the panels, and either way it is the combined output that counts. A solar array that sat comfortably under the threshold can tip over it when a battery is added, at the start or years later. That does not stop the project, but it adds an application and a wait before connection. Ask the installer which route applies and who will handle it; the detail is on grid connection.
Hybrid or AC-coupled
There are two common ways to connect a battery. In a hybrid arrangement, a single inverter manages both the panels and the battery, which suits a new installation where both are planned together. In an AC-coupled arrangement, the battery has its own inverter and joins the house wiring alongside an existing solar system, which suits adding storage to panels that are already working. Neither is better in every case. The choice affects the grid application, where equipment can go, and how easily the system can be extended later.
MCS and batteries
MCS treats battery storage as a technology in its own right, separate from solar PV. A firm can hold certification for solar panels without holding it for batteries. Before you agree to a battery, search the MCS installer directory and check that the technologies listed against the firm include battery storage as well as solar PV. If the battery is joining a system that someone else installed, ask how the new work will be documented alongside the original paperwork.
VAT on a battery
Under HMRC’s VAT Notice 708/6, solar panels and batteries supplied and installed in a home are charged VAT at 0% until 31 March 2027, after which the rate rises to 5% on 1 April 2027. The relief applies to equipment supplied and installed together, so a battery bought on its own and fitted by someone else may be treated differently; the notice sets out the conditions. A quote should show the VAT line clearly, and if your work might slip past the end of March 2027, ask how it will be charged.
Where it goes and how you keep an eye on it
A battery needs a place that suits the equipment and the house: commonly a garage, a utility room or an outside wall. Ask why the proposed spot was chosen, how the unit is ventilated and protected, and how it can be isolated if work is ever needed. Ask too what monitoring comes with it, so you can see how much it stores and releases in each season and judge whether it is doing the job you bought it for.
Questions to ask before buying a battery
- How much surplus do you expect my array to produce each month, and how much would the battery capture?
- Will the combined inverter output exceed 3.68 kW on my supply, and if so, who makes the G99 application?
- Does your MCS certification cover battery storage as well as solar PV?
- Would you set it to charge from the grid overnight, and on what kind of tariff does that make sense?
- Where will it go, and why there?
- What paperwork will I receive for the battery, separate from the solar certificate?
For the general checks on any firm, see choosing an installer. Households that heat with oil face a different set of questions, covered in off-gas homes around Northwich.
This page deliberately gives no battery prices, brands or lifespans. They vary widely and change quickly; get them in writing from the installer and check them against the manufacturer’s own documents.