Portable generator backup in the UK: safe siting and sizing

A portable fuel-burning generator can support selected appliances during an outage, but only if you have a suitable outdoor operating location, safe connections and a fuel plan. If those conditions cannot be met, choose another backup approach. A generator is not a safe indoor alternative to a battery.

First question: do you have a safe place to run it?

Generators belong outdoors, well away from doors, windows, vents and other openings. Never operate one in a home, garage, shed, tent, caravan or other enclosed or partly enclosed space. An open garage door, fan or carbon-monoxide alarm does not make such a location safe. Exhaust can enter neighbouring accommodation as well as your own. HSENI's emergency-generator advice warns that carbon monoxide is colourless and odourless, and that partial ventilation is not enough.

Check the manufacturer's siting and clearance instructions and assess where exhaust will go, including when the wind changes. A balcony, narrow courtyard or doorway is not automatically a suitable outdoor site. If you cannot keep exhaust away from people and openings, do not use the generator there. Battery-powered CO alarms installed and maintained as instructed provide an additional warning, not permission to choose an unsafe site.

Keep the unit on a stable surface and protect it from rain and standing water without enclosing it or restricting cooling and exhaust dispersal. Do not improvise an exhaust hose or wrap the generator in a cover while it runs. Keep children, pets and flammable materials away. Hyundai Power Products' current safety guidance reinforces outdoor siting and the dangers of improvised exhaust extensions.

What should it power?

Make a short list of essential appliances rather than trying to run everything. Small lights, charging and communications may be simpler to support with a battery power station. Fridges, pumps and other motors need particular attention to starting demand. Medical equipment requires a plan agreed with its supplier; do not treat a portable generator as an independently verified life-support supply.

1. Record each appliance's normal input power and any manufacturer-stated starting demand.
2. Add the running loads that will operate together.
3. Check the worst relevant starting event while other loads are running. Staggering starts helps only where the appliances and operating plan allow it.
4. Compare against the generator's rated continuous output and permitted peak output and duration. Check each socket's limit as well as the total.
5. Confirm the exact UK variant, voltage, frequency, plugs, waveform suitability and the appliance manufacturer's requirements. Do not treat a kVA rating as identical to usable kW for every load.

Illustrative arithmetic: suppose a fridge is specified at 120W running and 800W starting, alongside a 300W charger and 20W of lighting. Running demand is 440W. If the fridge starts while the others run, demand is 1,120W. The 800W starting figure replaces, rather than adds to, the fridge's 120W running figure in that scenario. These are hypothetical loads for a worked example, not specifications for an actual fridge or a recommendation for a particular generator. Obtain the real figures and suitable margin from the manufacturers.

Appliance supply is not household wiring

Use only the appliance connection arrangements permitted by the generator's instructions, with suitable undamaged, correctly rated leads and protected connections. Keep electrical connections dry and avoid trip hazards or trapped cables. Have a competent electrician resolve protection, earthing or connection questions; adding a generic accessory is not proof that a system is safe.

Never plug generator output into a household wall socket. Never use a male-to-male lead or attempt DIY mains changeover wiring. Backfeeding can expose network workers and other people to lethal voltage. Supplying a building's fixed circuits requires competent electrical design and installation of appropriate isolation, changeover, earthing and protective arrangements. Honda's generator safety guidance explains the utility-backfeed hazard and the requirement to isolate a building supply from utility lines; it is safety guidance, not a UK wiring design.

Fuel, refuelling and maintenance

• Use the specified fuel, oil and maintenance schedule. Check the manual before first use; do not assume a newly delivered generator is ready to start.
• Turn it off and let it cool before refuelling. Refuel outdoors, away from ignition sources, and deal safely with spills before restarting.
• Store fuel in suitable labelled containers outside living areas, away from heat or ignition sources, and follow applicable fuel-storage rules and the manufacturer's advice.
• Plan safe access and handling in darkness. Do not let urgency turn hot refuelling into a routine.
• Follow the manufacturer's storage procedure when it is no longer needed. Do not assume stored fuel remains suitable indefinitely.

These precautions follow HSENI's fire and fuel guidance. No fuel price, storage quantity entitlement or engine runtime is assumed here; these depend on the product, fuel and circumstances.

If an alarm sounds or someone feels unwell

Move everyone into fresh air immediately if carbon-monoxide exposure is suspected; do not delay to investigate or retrieve equipment. Seek urgent medical help and explain the possible exposure. Call 999 for serious illness or immediate danger. Do not re-enter until it is safe to do so on professional advice. The manufacturer's safety page identifies sickness, dizziness and weakness as warning signs and advises immediate fresh air.

Make a usable plan before an outage

Practise the manufacturer's start, load and shutdown procedure in a suitable location, record the permitted appliance combination and keep the instructions accessible. Do not test in a garage to avoid disturbing neighbours. If the site or procedure cannot be made safe, use lower-power battery equipment and your household emergency plan instead. Start with the power-cut checklist for needs that do not require a generator.