Battery types, cold weather and where to put a home battery

The main types of home battery

Every home battery stores electricity in cells. What differs is the chemistry inside the cells, which affects how safe the battery is, how it copes with cold, how long it lasts and what it costs.

Swipe the table sideways to see all four types.

Cycle figures are typical manufacturer claims. One cycle is one full charge and discharge, so a battery used once a day does about 365 cycles a year. Always check the warranty for the battery you are offered.

Is a Tesla battery lithium? Yes. Tesla’s Powerwall batteries are lithium-ion. The current Powerwall 3 uses LFP cells. The older Powerwall 2, still found in many homes, used NMC.

LFP, LiFePO4 and “LiFe” are the same thing. All three mean lithium iron phosphate. It is a kind of lithium-ion battery, not an alternative to it.

Sodium-ion batteries use sodium, the element in table salt, instead of lithium. The raw materials are cheaper and more plentiful, they work much better in the cold, and they give off less heat if something goes wrong. The drawbacks: they store less energy for their size and weight, so units are bigger; only a few products and installers are available in the UK so far; and there is less long-term evidence of how they age. They are worth watching, but LFP is the mainstream choice today.

Lead-acid is the old technology used in car batteries. It is rarely used for new home systems now because it is heavy, wears out quickly and is damaged if you empty it too far.

What home batteries really cost in 2026

The Energy Saving Trust says a home battery can cost £1,500 to £10,000, and that a 5 kWh system costs around £4,600 (its page was last updated on 19 August 2026). That is a fair guide for a small battery, but the price per kWh of storage has fallen, and bigger batteries cost much less per kWh than small ones.

• Installed battery, about 10 kWh: typically £4,000 to £6,500 in 2026, or around £400 to £650 per kWh. This is the most common size, and the Energy Saving Trust says a typical home system is around 10 kWh.
• Small installed battery, about 5 kWh: around £2,500 to £5,500, which is more per kWh.
• Premium all-in-one systems, such as the 13.5 kWh Tesla Powerwall 3: around £7,400 to £11,000 installed.
• A bare battery module bought online: from about £120 per kWh. For example, a 16 kWh LFP module was advertised at about £1,900 in October 2026.

Why is a bare module so much cheaper? Because it is only the battery. To use one safely and legally you also need:

• an inverter that works with that battery (a hybrid or battery inverter), which costs extra;
• wiring, isolators and protection fitted by a qualified electrician;
• your network operator to be notified (G98 or G99), like any other battery;
• a location and a casing that meet the fire-safety rules below;
• VAT: the 0% rate only applies when a battery is installed for you, so a battery bought on its own carries 20% VAT.

To check a price against your own electricity use, try our battery size and payback calculator. It starts with a 10 kWh battery at a typical 2026 installed price, which you can change to your own quote.

Cold weather: why a battery can stop charging

Lithium batteries, including LFP, must not be charged when their cells are below about 0 °C. Charging a frozen cell can damage it permanently and, in the worst case, make it more likely to fail later. So the battery’s own management system blocks charging until the cells warm up. It can usually still supply power below freezing, but less of it.

This matters in the UK because the cheapest time to charge is overnight, and winter nights are the coldest. A battery that will not charge in a cold snap misses the cheap rate on exactly the days you most need it.

Before you buy, check:

1. The charging temperature range on the specification sheet, not just the “operating” range.
2. Whether it is built for outdoor use in the cold, and how. Some have heaters or other temperature control. Tesla, for example, rates the Powerwall 3 to work outdoors from −20 °C to 50 °C. A heater uses a little of the stored energy.
3. Where it will actually go. A cheap module meant for indoor use should not go on an outside wall or in a cold shed or detached garage.
4. Heat as well as cold. Many batteries lose performance above about 40 °C, so avoid spots in strong direct sun.

Where a battery can and can’t go: the fire-safety rules

A battery fire is hard to put out and gives off toxic gases, so the location matters. The British Standards Institution’s PAS 63100:2024 sets out where home batteries can go. It is a standard rather than a law, but MCS-certified installers follow it through the IET Code of Practice that the MCS battery standard refers to.

A battery must never go in:

• a bedroom, or any room where someone sleeps;
• an escape route: a hallway, stairs, landing, corridor or lobby;
• a loft, roof space or other void;
• a cellar or basement with no way out to the outside.

Usually suitable, if your installer agrees:

• an outside wall, at least 1 m from doors, windows, escape routes and vents, and 2 m from anything flammable such as fuel storage, with impact protection if it is next to a driveway (and check how it copes with cold);
• a garage or outbuilding;
• a utility room or a similar room that is not an escape route.

Other rules that apply:

• Each battery unit can be up to 20 kWh. The total in a home can be up to 40 kWh, or 80 kWh if the batteries are outside, in a detached garage, or in an attached garage with 60-minute fire separation from the house.
• The battery’s case must be non-combustible, such as steel.
• If a battery goes in a cupboard or a room you rarely use, a smoke or fire alarm must be fitted there and linked to your home’s other alarms.
• Tell your home insurer. If you rent, or own a leasehold flat, get written permission first. See Renting and solar panels.

Are sodium-ion batteries exempt from the fire rules?

No. Sodium-ion batteries are less likely to overheat and give off less heat if they do fail, which is a real safety advantage. But most still contain a flammable liquid inside the cells, so they can still burn if they are badly damaged or faulty. PAS 63100 covers home batteries of every chemistry and does not exempt any of them.

So the same rules apply as for lithium: never in a bedroom, the loft, an escape route or a cellar with no outside door, with the same size limits and alarm rules. Your installer and insurer will treat a sodium-ion battery the same way.

Where sodium-ion can really help is the cold. In tests, some keep about 90 to 95% of their capacity at −20 °C, compared with roughly 50 to 70% for LFP. That could make sodium-ion a good choice for an outbuilding once more certified products and installers are available. Some sodium-ion products still limit charging below 0 °C, so check the specification sheet.