Home Battery Storage: Does It Keep the Lights On?

A fixed home battery can keep the lights on in a power cut, but only if the system is designed and configured to work independently of the electricity grid. The government's emergency preparedness guidance is clear on this point: if you have solar panels and a battery storage system with power backup capability, some installations can continue to provide power during a power cut, which may help keep essential appliances running during an outage¹. A battery installed without that capability, which is how many are set up, will shut down with everything else when the grid goes down.

It is also worth keeping the risk in proportion. For a short power cut, a torch, a charged power bank and a power station may be all you need. A fixed battery earns its place for longer outages, for households that rely on powered medical equipment, and for homes that want to use their own solar power in the evenings. This page explains what size of battery suits which home, what backup modes do, how solar and batteries work together safely, and where lithium-ion batteries, the chemistry inside almost all of them, become a fire risk and what to do about it.

What size battery your home needs

Sizing a home battery comes down to what you want to keep running and for how long. A useful starting point is the household: a one or two bedroom home is generally matched by around 3 kWh to 5 kWh of storage, enough to keep lighting, a router, phone charging and a fridge going through a typical outage. Larger homes, with more people, more appliances and often a higher baseline demand, need more: 8 kWh to 10 kWh is the usual range quoted for whole-home cover.

Makers do not entirely agree on where the lines sit. One product page recommends 3 kWh to 5 kWh for smaller households while another recommends 8 kWh to 10 kWh for the same kind of home, so treat these figures as a range to discuss with an installer rather than a fixed rule. What matters more is the load you actually want to support. Work out which circuits matter to you, using our guide to deciding what to keep running when the mains fails, and size from there. If you want to understand the units involved, watts, watt-hours and surge explains how capacity translates into running hours for real appliances.

Two things change the picture. First, a battery paired with solar panels can recharge during the day, so a smaller battery can stretch across a multi-day outage if the weather cooperates. Second, a battery sized for day-to-day use, charging cheaply overnight and discharging in the evening, is not necessarily sized for backup: the two jobs overlap but are not the same. If backup is your main reason for buying, say so at the survey stage, because it affects both the capacity and how the system is wired, which we cover in connecting a generator or battery to your home's wiring.

Bear in mind too that most cuts are short⁵, and compensation exists for the longer ones: you can get £100 for homes, or £195 for businesses, if fewer than 5,000 properties are affected for more than 12 hours, or more than 5,000 properties are affected for more than 24 hours². The maximum payable where 5,000 or more properties are affected is £400².

Free battery packs and the Priority Services Register

If someone in your household depends on electricity, for medical equipment, for a landline they rely on, or because of age, disability or illness, sign up to your energy supplier's Priority Services Register. It lets your supplier and network operator know that you need additional support during a power cut¹, and the register is designed to keep the most vulnerable customers up to date in a cut and provide additional support if needed⁶.

This is not just a courtesy list. If you are on the Priority Services Register, contact your supplier directly to ask what extra help yours provides, because what each company offers will be different. If you rely on powered medical equipment or would be particularly vulnerable in a power cut, ask to join the register, and check whether any scheme offering battery packs is open to you in your area.

The landline switchover adds another reason to be on the register. Digital landlines cannot carry a power connection, so handsets and routers must be powered from your home supply and will not function in a power cut unless you have a backup power system such as a battery or generator⁷. If your landline will not work during a power cut, your landline provider might offer you a free solution, such as a back-up battery unit, for a minimum of one hour, so you can still call the emergency services¹. Ofcom confirms the back-up must last for at least one hour in a power cut, and some providers have back-ups that last up to seven hours³. For vulnerable customers with an analogue landline, the provider must provide a free back-up battery unit, meaning the landline would work for at least an hour during a power cut, and many batteries now last much longer⁸.

If you rely on powered medical equipment, our page on powering CPAP, oxygen and other medical devices from a battery sets out the practical options.

Solar panels and a battery: installation that keeps the system safe

Solar panels on their own do not run your home in a cut, because a standard grid-tied system shuts down when the grid does, to protect engineers working on the lines. The combination that does work is solar panels plus a battery storage system with power backup capability: some installations can continue to provide power during a power cut if they are designed and configured to operate independently of the electricity grid, which may help keep essential appliances running during an outage¹. Whether yours can do this depends on the inverter and the wiring, so it must be specified before installation, not assumed afterwards. Our page on whether home solar panels work in a power cut covers the detail.

The safety of the whole system rests on the installation. Electrical Safety First, the UK's electrical safety charity, says it is vitally important to use a skilled, trained and qualified solar PV installer who is registered with a competent person scheme, and that companies registered with MCS also offer an additional level of assurance⁹. Reputable installers should also be signed up to a consumer code, such as the RECC, which helps prevent pressure-selling tactics⁹.

Once installed, the system needs occasional attention:

• Have the system inspected and tested at least every five years to ensure it remains safe⁹
• Do regular visual checks for cracks, breaks, loose connections, and cable damage caused by vermin and weathering⁹
• Do not ignore burn marks, arcing sounds, buzzing or crackling, fuses blowing, circuit-breakers tripping, or anything that feels hot to touch: unplug and contact the retailer, manufacturer or a qualified repair technician⁹

The fire risk from solar panels themselves is low, but known problems can occur through bad installations, poor quality connections and cable damage through vermin and weathering⁹, which is why the visual checks above matter. Cleaning plays a part too. Most panels have a self-cleaning coating which, when installed at a suitable angle, allows rain to clear dirt and debris⁹. Periodic cleaning by a specialist company can remove accumulated dirt, dust and debris, including lichen and guano, improving sunlight absorption, maximising energy production and preventing hotspots which can result in a panel failing; Electrical Safety First says this could increase energy production by up to 15 per cent⁹.

Plug-in solar panels: what they change for households

Plug-in solar panels, small panels that feed electricity into your home through a normal socket, have attracted growing interest. In principle they are simple: light from the sun hits the panels and generates energy, which flows into the electrical circuit for the home, providing electricity. They will not generate enough energy to power your home entirely, so treat them as a supplement rather than a substitute for mains power or a battery.

The regulatory position is the sticking point, and it is changing, so check the current rules before you buy. If you are considering plug-in solar, check that any product you buy meets the current specification, use a skilled, trained and qualified solar PV installer registered with a competent person scheme where installation is needed¹⁰, and read our page on whether plug-in solar panels are safe to connect.

For charging a portable power station rather than feeding the house wiring, ordinary portable solar panels avoid these regulatory questions entirely, because they charge a battery rather than supplying the home's circuits.

Where lithium-ion batteries become a fire risk

Home batteries, power stations, power banks, phones, laptops, vapes, e-bikes and e-scooters all rely on lithium-ion cells. They are lightweight, energy dense and long-lasting, but can be more volatile than traditional batteries¹¹. Fire services across the UK report an increase in the number of fires caused by lithium-ion batteries¹², and warn that lithium-ion battery fires are particularly dangerous as they are instantaneous and explosive in nature, potentially compromising escape routes¹³.

The causes are consistent across every fire service that publishes guidance. Devon and Somerset Fire and Rescue Service lists the conditions that turn a battery into a hazard: overcharging, short circuits, water submersion and physical damage¹². Fires can result from overcharging batteries, charging devices on flammable surfaces such as on a bed or under a pillow, using batteries that are not recommended by the manufacturer, and exposing them to hot temperatures or water¹⁷. Lithium-ion batteries in phones, vapes, e-bikes and e-scooters can become a fire risk when exposed to high temperatures or charged incorrectly¹⁸. Misuse, such as unsafe charging or product modifications, can significantly increase fire risks¹⁹.

Many of these fires happen at the worst possible moment. Many happen in homes while batteries are charging²⁰, and fires often occur when charging the batteries²¹. Covering devices while charging traps heat and increases fire risk¹¹. Cheap chargers and batteries may not meet UK safety standards and can be dangerous¹¹. A damaged lithium-ion battery can fail unexpectedly and start a fire²², and damaged or end-of-life batteries thrown into household waste can be crushed or punctured, releasing flammable electrolytes into the air which can trigger explosions and rapidly spreading fires¹⁷.

Disposal is part of the same picture. Lithium-ion batteries should never be placed in household waste¹⁵, and when punctured or crushed they can cause fires in bin lorries, recycling and waste centres¹⁴. Incorrectly placing them in general household and recycling waste can lead to significant waste fires¹². Tape over the terminals with electrical tape to prevent short circuits¹¹, and check your local authority's website or the recycle your electricals website for the safe way to dispose of lithium-ion batteries in your area²³. Most local recycling centres accept lithium-ion batteries alongside Waste Electrical and Electronic Equipment items¹⁵. Our page on how to dispose of a damaged lithium battery gives the full procedure.

What to do if a battery overheats or catches fire

The warning signs are consistent: a battery getting unusually hot, swelling or bulging, hissing, or showing other damage. If a battery shows signs of overheating, swelling or other forms of damage, do not use the battery; dispose of it appropriately and report the defect to the manufacturer¹². If a vape battery gets unusually hot, starts to bulge or starts hissing, stop using it immediately and leave it in a safe place until you can dispose of it properly²⁴. If a battery shows signs of swelling, overheating or emitting smoke, safely remove it and report the incident to the appropriate authorities¹⁷. Our page on warning signs a lithium battery is dangerous lists what to look for.

If a battery catches fire, do not tackle it yourself. Call 999 and ask for the Fire and Rescue Service¹⁶. The reason fire services are so firm about this is the behaviour of the fire itself: battery fires can spread quickly, are difficult to extinguish and can reignite after appearing to have gone out²⁵. When damaged or crushed, batteries can ignite without warning²⁵. A fire that seems out can come back, which is why firefighters may need to keep a battery under observation after the flames are doused.

Prevention is mostly a matter of charging habits:

• Charge devices and equipment during the day, instead of at night while you are sleeping, and charge them away from escape routes¹²
• Never leave batteries unattended while charging and do not charge them overnight¹⁷
• Always use the charger that came with your device or a genuine replacement from a trusted supplier¹¹
• If you notice any damage or wear and tear on your charger, replace it with an official charger from a reputable source¹⁵
• Use the correct charger for the equipment, as conversion kit guidance stresses²²
• Do not charge on flammable surfaces such as a bed or under a pillow¹⁷

Our page on whether it is safe to charge overnight and the safe battery charging at home checklist go through the setup in detail, and lithium-ion battery safety at home covers the whole subject.

Storing a spare battery safely

If you keep a spare battery, a power station, expansion pack or loose cells, store the product and its batteries in a cool place, avoiding exposure to extreme heat or cold¹⁵. Heat is the enemy: high temperatures are one of the conditions that turn lithium-ion batteries into a fire risk¹⁸, and leaving a battery in a hot loft, a sunny conservatory or a car in summer works against you. Follow the manufacturer's instructions for the storage and maintenance of lithium-ion batteries if they are not going to be used for extended periods of time¹⁴, since makers know their own cells' tolerance best.

Check stored batteries periodically for the damage signs above, because a battery that fails in storage can do so without warning¹⁴. When a stored battery reaches the end of its life, the disposal rules in the fire risk section apply: never household waste, terminals taped, taken to a recycling centre¹⁵. Our page on how to store a power station when not in use covers the practicalities for the larger units.

What to have ready regardless of your battery

However capable your fixed battery is, keep a simple kit that works even if the battery or its inverter fails. The essentials that could help you cope with a power cut are battery candles, torches and batteries, and a mobile phone power pack²⁶. Make sure you have multiple torches along with extra batteries²⁷, and include a battery-operated torch and spare batteries, or a wind-up torch, in your home emergency kit²⁸. Save key documents and information in a safe place, know where you can find a torch, and consider getting a separate battery charger¹⁰.

During the cut itself, use battery-operated lights or torches as an alternative light source²⁹, and use your devices sparingly to conserve battery power until you can charge them again⁸. Firefighters can be called to fires started by candles or portable heaters during a power cut²⁹, so torches are the safer light. Report the cut by calling 105⁴, and if you are on the Priority Services Register, your supplier should be in touch. The full procedure is in our power cut backup power checklist and the power cuts household guide.

Questions people ask

Do I need a G99 certificate to install a home battery? Any system connecting to your home wiring must meet the grid connection standards, and the connection arrangements differ between smaller plug-in systems and larger fixed installations. Use a skilled, trained and qualified solar PV installer registered with a competent person scheme¹⁰: your installer should handle the connection paperwork and confirm it before the system is energised.

How often should solar panels be inspected? Have the system inspected and tested at least every five years to ensure it remains safe, and do regular visual checks yourself for cracks, breaks, loose connections and cable damage⁹.

Do solar panels need cleaning? Most have a self-cleaning coating that lets rain clear dirt when they are installed at a suitable angle, but periodic specialist cleaning removing dirt, lichen and guano could increase energy production by up to 15 per cent and prevents hotspots that can cause a panel to fail⁹.

How do I spot a solar cold caller? Be suspicious if you are contacted out of the blue or put under pressure to buy quickly, especially with time-limited or one-off discounts; watch out for extremely short payback times and low prices that may not include all necessary parts and services. Use an installer registered with a competent person scheme, ideally MCS certified, and signed up to a consumer code such as the RECC⁹.

Is it safe to charge batteries overnight? Fire services advise charging during the day instead of at night while you are sleeping, charging away from escape routes, and never leaving batteries unattended while charging¹².

Should I use a cheap replacement charger? No. Always use the charger that came with your device or a genuine replacement from a trusted supplier; cheap chargers and batteries may not meet UK safety standards and can be dangerous, and a damaged charger should be replaced with an official one from a reputable source¹¹.

Can a battery fire restart after it has been put out? Yes. Battery fires spread quickly, are difficult to extinguish and can reignite after appearing to have gone out, which is why you should call 999 and ask for the Fire and Rescue Service rather than tackling one yourself²⁵.

Will my landline work in a power cut after the digital switchover? Digital landlines cannot carry power, so handsets and routers will not work in a cut without backup power; providers may offer a free back-up battery unit lasting at least one hour, and some last up to seven hours, while vulnerable customers must be provided with one⁷.