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Be ready for a three-day power cut. A home battery, no solar needed.
The government’s Be Ready campaign asks every household to plan for three days without power. A home battery keeps the fridge, boiler, lights and Wi-Fi on, and saves you money the rest of the year.
The checklist covers water, tinned food, a torch and a power bank. A home battery covers the bit a power bank can’t: the fridge and freezer, the boiler, the lights, the Wi-Fi. And for the rest of the year it pays its way by storing cheap overnight electricity for you to use at the expensive times of day.
You don’t need solar panels
A battery is a separate piece of kit. It charges from the grid overnight on a cheaper tariff, or from solar panels if you have them or add them later. Plenty of homes can’t have solar: a shaded or north-facing roof, a flat, a listed building, a conservation area. A battery still works for all of them. It usually goes in the garage, a utility room or on an outside wall, near the fuse board.
Will it keep the lights on in a power cut?
Only if it’s set up to. This is the question to ask any installer. When the grid goes off, a battery has to disconnect your home from the network (so it isn’t feeding power back to engineers working on the cables) before it can power anything. Many systems sold on price simply switch off with the grid. To keep running, a system needs a backup unit or gateway that does that switch-over automatically, usually within a few seconds.
- Essential circuits backup: the fridge and freezer, the boiler, lights, the router and a few sockets are wired to a backed-up board. Lower cost, and the battery lasts longer.
- Whole-house backup: everything stays on, within what the battery and inverter can deliver at once. Costs more and drains the battery faster.
We’ll tell you which suits your home and quote for it in writing, so you know exactly what stays on.
How big a battery for three days?
Rough figures for a typical home running only the essentials (yours will differ, and the survey sizes on your own usage):
- Fridge-freezer: about 1 kWh a day
- Gas boiler and heating pump (it needs electricity to run): about 1 kWh a day in winter
- LED lights in the rooms you’re using: about 0.5 kWh a day
- Broadband router, phones and a laptop: about 0.5 kWh a day
That’s roughly 3 kWh a day, or 9 to 10 kWh for three days. Without solar, the battery can’t recharge until the power comes back, so size for the whole stretch. Electric showers, ovens, kettles and electric heating use far more, and are usually left off the backed-up circuits.
Home batteries compared, cheapest first
If you are choosing a battery because of the Be Ready advice, the row that matters most is power cut backup: whether the battery keeps your home running when the grid goes off, and what extra equipment that needs. Here are six popular batteries side by side. The four we fit are marked. For the others, ask us: some need a specific approved installer.
| Battery | Cost | Usable size | Power cut backup | Warranty | Good to know |
|---|---|---|---|---|---|
| AlphaESS SMILE G3 Ask us | £ | 4.56 or 9.3 kWh per module | Backup port for chosen circuits; switch-over of 20 milliseconds or faster is quoted | 10 years, 80% at year ten | Hybrid or AC-coupled. Check the warranty terms: some depend on the battery staying online. Budget choice. |
| Fox ESS EVO We fit | £ | About 9.7 kWh | Backup port for selected circuits included; whole-house needs an extra backup box | 12 years | Battery and inverter in one outdoor-rated unit, with a 5, 8 or 10 kW inverter. Good value for its size. |
| Tesla Powerwall 3 We fit | ££ | 13.5 kWh | Whole or part of the home, with Tesla’s Backup Gateway | 10 years, 80% at year ten | Built-in inverter up to 11 kW. The biggest single unit here, so the highest total cost. Needs a Tesla-certified installer. |
| Sigenergy SigenStor We fit | ££ | 5.2 or 7.8 kWh per module, stackable | Whole-home with the Sigen Gateway (an extra) | 10 years, 70% at year ten (or a throughput limit) | Inverter, battery and, if you want it, an EV charger in one stack. Grows by adding modules. |
| Enphase IQ Battery 5P Ask us | ££ | 5 kWh per unit, stackable | With the Enphase IQ System Controller | 15 years or 6,000 cycles | AC-coupled, so it suits homes that already have Enphase solar. Small units, so a three-day target needs two. |
| SolarEdge Home Battery We fit | £££ | 9.7 kWh | Backup is available with SolarEdge’s backup equipment; we confirm what stays on at survey | 10 years, 70% at year ten | DC-coupled and designed to pair with a SolarEdge inverter. The battery alone sits at the top end; the installed price is not published. |
£, ££ and £££ rank these six by fitted cost for each kWh of storage: £ is the cheapest. A bigger battery costs more in total, so a Powerwall can cost more than a smaller unit even where its cost per kWh is lower. We show bands, not prices, because prices change often and differ between sellers. Figures are the makers’ published specifications and public price roundups, checked November 2026, so treat them as a guide. Sources: Home Energy Quotes, Solar Grid Check, Heatable.
How to choose for a power cut
- Ask what backup costs. On several of these the backup unit or gateway is an extra, often around £1,000 fitted. Make sure it is in the quote.
- Match the size to the three days. About 9 to 10 kWh covers the essentials (see above). Two 5 kWh units or one 9 to 13 kWh unit both get there.
- Already have solar? Some batteries work best with a matching inverter (SolarEdge with SolarEdge, Enphase with Enphase). We check this at survey.
- Check the warranty small print. Years matter less than the capacity it must keep and whether it depends on staying online.
Not sure which is right? Fill in the battery survey and we will recommend one and quote it in writing.
0% VAT until 31 March 2027
A battery added to an existing home is currently zero-rated for VAT, whether or not you have solar panels. That relief is set to end on 31 March 2027, so a system fitted before then avoids the VAT.
How it works with us
- Tell us about your home. The battery survey below, a call, or an email. Photos of where it could go and your fuse board help most.
- Survey and sizing. We look at your usage, your tariff, your fuse board and where the battery can go, and agree which circuits are backed up.
- A fixed, written quote. Battery, backup unit, installation and any fuse board work, itemised.
- Installation by our own engineers. Usually one day. We notify the network operator for you (UK Power Networks in Hertfordshire and London) and certify the work.
- We test a power cut before we leave. We switch off the supply and show you what stays on, and set up the app so you can see the battery’s charge.
We fit systems such as Sigenergy, SolarEdge, Fox ESS and Tesla Powerwall, and can add solar panels or an EV charger now or later. See solar PV and battery storage.
While you’re getting ready
- Work through the government’s Be Ready checklist. Our short guide: the Be Ready campaign and power cuts.
- If someone at home relies on medical equipment, or is elderly or disabled, join the free Priority Services Register through your energy supplier.
- Save 105 in your phone: the free number for power cuts. And see no power, or only half of it for what to check first.
Questions we’re asked
Can I have a home battery without solar panels?
Yes. A battery charges from the grid, usually overnight on a cheaper tariff, and you use that stored electricity during the day and in a power cut. You can add solar panels later and the battery will store their power too.
Does every home battery work during a power cut?
No. Many systems switch off when the grid goes down. To keep power on, the system needs a backup unit or gateway that disconnects your home from the network and switches over automatically. Ask any installer this before you buy.
How big a battery do I need to get through three days?
Running only the essentials (fridge-freezer, gas boiler, lights, router and phones) a typical home uses roughly 3 kWh a day, so about 9 to 10 kWh for three days. We size it on your own usage at the survey.
Will my gas boiler work in a power cut?
Not without electricity. The boiler's controls and the heating pump need power. If the boiler is on a backed-up circuit, a battery keeps your heating and hot water running.
Is there VAT on a home battery?
A battery retrofitted to an existing home is currently zero-rated for VAT, with or without solar panels. That relief is set to end on 31 March 2027.
Do I need permission to fit a battery?
Not planning permission in most cases, but the network operator must be told. We handle that notification for you as part of the installation.
Can I add more batteries to my existing system?
Often, yes. Most modular systems take extra battery modules up to a limit set by the inverter or battery controller, so a 10 kWh system can usually grow to 15 or 20 kWh with the same brand. We check the model, the loft or cupboard space and the weight, then quote for the extra modules and the network notification.
Written by SEGplc. Last updated 4 November 2026.
Battery survey: send us the details and photos
About five minutes on your phone. Tell us about your home, then add photos of where the battery could go, your fuse board and your electricity meter. We do a desktop survey and come back with a fixed, written price, usually without a first visit. Skip anything you’re not sure about.
Need it done by a date?
Tell us the deadline. We’ll tell you honestly whether we can hit it — and we usually can.