Immediate danger to life: call 999 or 112.

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Using backup power safely

Sources checked 13 October 2026

Action summary

1. Start by listing the equipment you need to keep working and its actual electrical requirements.
2. A planning calculation: A 500 watt-hour battery with an assumed 80% usable energy has 400 watt-hours available.
3. Use batteries and chargers specified for the equipment.
4. Portable fuel generators

Start by listing the equipment you need to keep working and its actual electrical requirements. Ask the supplier about medical-device compatibility and use approved backup arrangements. A power bank useful for a phone may not support a fridge or medical device. Runtime depends on load, capacity, efficiency, temperature and battery condition.

A planning calculation: A 500 watt-hour battery with an assumed 80% usable energy has 400 watt-hours available. At a steady 20-watt load, the arithmetic estimate is 20 hours; at 100 watts, it is 4 hours. The 80% factor is an illustrative assumption, not a product specification. Starting surges and real conditions can reduce runtime. Do not use this calculation to certify life-support cover.

Use batteries and chargers specified for the equipment. Follow manufacturer instructions on loading, ventilation, temperature and charging. Keep them dry, uncovered and away from escape routes. Stop using a swollen, damaged, unusually hot or smoking battery. If there is fire or dangerous smoke, get to safety and call 999; do not attempt to manage a major lithium battery fire yourself.

Portable fuel generators

• Operate outside, away from openings which can admit exhaust. Never use one in a home, garage, tent, basement or partly enclosed space, even with a door open.
• Use appropriate electrical equipment and stay within the permitted load. Keep connections protected from water according to the manufacturer's instructions.
• Never connect a generator to a household socket or improvise a cable to energise your house. A building connection requires a properly designed installation by a qualified person.
• Shut down and let the generator cool before refuelling. Store fuel outside living areas in suitable containers and follow current fire-safety requirements.
• Use working carbon monoxide alarms in the home, but do not treat an alarm as permission to operate a generator in an unsafe place.

If you cannot provide a safe outdoor operating location, choose another solution. A balcony, small light well or enclosure beside neighbours' windows may not safely disperse exhaust. Confirm solar battery backup with your installer; panels alone do not prove off-grid operation.

Sources

• UK Government Be Ready: Power cuts
• Health and Safety Executive for Northern Ireland: Safety Tips Using a portable generator in an emergency
• NHS: Carbon monoxide poisoning
• London Fire Brigade: Batteries and chargers fire safety at home
• Energy Saving Trust: Solar inverters technical note

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