Using backup power safely

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.