Portable Generators: Petrol, Diesel, Dual-Fuel and Inverter Types

A portable generator is an engine that makes electricity, and for a household facing a long power cut it can keep a fridge cold, a phone charged and a few lights on. Clarke's guidance is that a generator can provide temporary emergency power during a power cut, with smaller models supporting selected items such as lighting, phone chargers, a refrigerator or freezer, and larger models running additional equipment within their rated capacity¹. But a generator is also the most demanding piece of backup kit you can own, because it burns fuel, makes exhaust and produces serious electrical output. The Health and Safety Executive warns that using petrol powered equipment such as generators indoors or in enclosed spaces can create significant levels of carbon monoxide which can kill even after a few minutes².

So before anything about brands or outputs, two rules come first. Never run a generator inside your home, garage or any enclosed space. And never connect one to your household wiring yourself: if you connect your own generation, this must be done by a qualified professional³. If the power is already off, call 105 for free and you will be put through to your electricity network operator⁴. This page explains the types of generator you can buy in the UK, what each does well, and how to use one safely.

Where a generator must never go

A generator lives outdoors, and the reason is its exhaust. The Health and Safety Executive's advice is to locate petrol generators outside in well-ventilated spaces so that fumes disperse and cannot gather or drift into building openings². Clarke's generator guidance says the same thing in practical terms: keep it outdoors and well away from doors, windows and vents, and never operate a generator inside a house, garage, shed, tent or caravan¹. A garage with the door open, or a doorway with the machine just outside, is not good enough, because exhaust can still pool or drift back inside through the opening.

The warning covers more than houses. nidirect's storm advice for Northern Ireland is blunt about standby generators: never use them indoors, as the fumes from the engine can be lethal⁵. The same advice applies in caravans, boats and mobile homes, where the risk of exposure to carbon monoxide from portable devices may be higher because the space is small and ventilation is poor⁶. London Fire Brigade's carbon monoxide guidance adds a related point worth knowing: carbon monoxide can travel through walls, which is why it also tells people never to take portable or disposable barbecues or charcoal burners into a home, tent, houseboat or caravan⁷.

When you site the generator, think about your neighbours as well as your own household. Position it on firm, level ground away from combustible materials, standing water and areas where exhaust gases could accumulate¹. That means not under a window of the house next door, not against a fence or stacked firewood, and not in a dip in the garden where fumes can settle.

Carbon monoxide, electric shock and fire: the three dangers

Carbon monoxide (CO) is the danger that kills most often, because you cannot see it or smell it. London Fire Brigade's after-a-flood guidance states the rule plainly:

London Fire Brigade⁸

The gas comes from burning fuel. NHS 111 Wales lists portable generators alongside gas boilers, gas or paraffin heaters and wood, gas and coal fires as appliances that can cause carbon monoxide poisoning⁹, and the Health and Safety Executive for Northern Ireland has warned that using kerosene heaters, charcoal grills and portable generators indoors can cause CO levels high enough to result in CO poisoning¹⁰. Wiltshire and Swindon Prepared's advice after flooding is the same: do not use petrol or diesel generators or other similar fuel-driven equipment indoors, because their exhaust gases contain carbon monoxide¹¹. Fit a carbon monoxide alarm in your home, and take any alarm, or any headache, dizziness or nausea that clears when you go outside, seriously.

Electric shock is the second danger, and it comes in two forms. The first is treating the generator's output casually: it is mains-level electricity from a socket, and it deserves the same respect as a wall socket in your home. The second is backfeed. Clarke's guidance is explicit: never connect a portable generator directly to household wiring or a wall socket, as this can create dangerous backfeed into the electricity network and may cause serious injury, fire or damage¹. Backfeed can energise the network outside your house and injure engineers working to restore your supply.

Fire is the third. A generator is a hot engine with fuel in it. Keep it away from combustible materials and standing water¹, and treat fuel storage with the same care. Devon and Somerset Fire and Rescue Service's winter guidance notes that equipment designed for outdoors, such as camping stoves and patio heaters, poses both a fire risk and a carbon monoxide risk when misused¹², and the same logic applies to generators. Refuel only when the engine is cool, and never store spare fuel or cylinders indoors: the Scottish Fire and Rescue Service advises storing spare gas cylinders outside where possible, and never in a basement, near drains, under the stairs or in a cupboard containing electric meters or equipment¹³.

Connecting a generator to your home: get an electrician

Running extension leads from the generator's own sockets to individual appliances is safe and simple, and it is how most households should use one. Wiring a generator into your home's fixed electrics is a different matter altogether. Wiltshire and Swindon Prepared puts it directly: it takes research by you, and the advice and expertise of a qualified electrician, for a generator to help you¹⁴. National Grid's advice on planned interruptions is that if you hire a generator, for safety reasons it is essential that it is connected by a qualified electrician³, and Northern Powergrid says the same: if you do choose to connect your own generation, this must be done by a qualified professional¹⁵.

The reason is not bureaucracy. A proper connection has to isolate your home from the network so that your generator cannot push power back up the cable, and it has to be done so that when the mains returns, the two supplies do not fight each other. That needs the right changeover equipment, installed and tested by someone qualified. Electricity North West's emergency power cut guidance adds a reality check for anyone imagining a generator as a whole-house solution: there will not be enough generators to keep everyone powered, and it may take longer to install and connect a generator to your local substation than the duration of the emergency power cut itself¹⁶.

One further point if you plan to run tools rather than household kit: some electronically controlled tools require a stable supply, so Clarke advises checking the tool manufacturer's guidance before connecting them to a conventional generator¹. If you want to go deeper on the wiring side, see connecting a generator to your home's wiring, and for the safe use of leads, see extension leads and overloading with backup kit.

Petrol, diesel or dual-fuel: how each fuel behaves

Most portable generators sold in the UK run on petrol or diesel, and some dual-fuel models add LPG from a cylinder. Each fuel behaves differently, and that shapes what the generator is good for.

Conventional petrol generators use an engine to drive an alternator at a relatively constant speed. Clarke describes them as practical for tools, lighting, pumps, workshop equipment and general site use, and notes that they often provide a higher output for the price¹. Which? gives an example of a petrol model with a fuel tank capacity of around 20 litres¹⁷. Petrol is the common choice for household backup because the machines are widely available and the fuel is easy to buy.

Diesel generators generally have a long running time, but Which? notes that diesel is more expensive to buy than petrol and can be noisier than petrol alternatives¹⁷. Diesel suits a household that expects very long outages or wants to run heavier equipment, and accepts the noise and bulk that come with the type.

Dual-fuel models run on petrol or LPG. The attraction for emergencies is that you are not dependent on one fuel: if petrol is hard to get after a storm, an LPG cylinder keeps you running. LPG brings its own handling rules, which are covered in LPG cylinders and regulators for dual-fuel generators.

Inverter generators: cleaner power for phones and laptops

An inverter generator is a petrol generator with electronics that clean up the output. Clarke's guidance explains that inverter generators electronically control and condition the power they produce, and that they are generally quieter, more compact and more fuel-efficient at lighter loads, which is why they are popular for caravans, camping, laptops, televisions, chargers and other sensitive devices¹. Many produce a pure sine wave output designed to closely replicate mains electricity, which makes them suitable for laptops, televisions, mobile devices, audio equipment, battery chargers and modern caravan electronics¹.

That last point is the whole reason to care. A conventional generator's output can be rough enough to trouble sensitive electronics, while an inverter model's smoothed output is designed to be safe for them. Briggs & Stratton says of its P2400 PowerSmart Series inverter generator that the inverter technology produces smoother power, so you can safely recharge and power sensitive electronics such as laptops, smartphones and gaming systems¹⁸.

Inverter models are also the quiet end of the market. Briggs & Stratton describes the P2400's 58dB operating volume as quieter than a normal conversation¹⁸, against diesel's reputation for noise¹⁷. Run time can be respectable at light loads: the P2400 can supply equipment for up to 8 hours at 25% load¹⁸. Sockets reflect the intended use: Which? notes inverter models with two 230V 13A sockets, a 12V DC outlet and two USB ports, and a suitcase-style model with two USB sockets for charging smaller items¹⁷.

If you need more than one inverter generator's output, some compatible models can be linked. Clarke's guidance says some compatible inverter generators can be connected using a purpose-designed parallel kit, which combines their output to provide additional capacity¹, and Briggs & Stratton offers an optional parallel connector kit for the P2400 that lets you connect two units together for more power¹⁸. For a fuller comparison of the two petrol technologies, see inverter generator or open-frame generator.

Power output: what the watts on the label mean

Generator output is usually shown in watts or kilowatts, with 1kW equal to 1,000W¹. Two numbers matter: a continuous rating, which is what the generator can supply steadily, and a maximum rating for short bursts. Clarke gives a worked example: a generator rated at 2,000W continuous and 2,200W maximum should normally be used below 2,000W¹. Plan your loads against the continuous figure, not the peak.

To judge whether a generator is big enough, add up the running watts of what you want to power at the same time. Electrical Safety First's appliance ratings give a sense of scale: a portable air conditioner can use up to 2000 watts, typically 900 to 2000W depending on its cooling power¹⁹. Against that, real generators on the UK market range widely: Which? lists a portable inverter generator at 3300W¹⁷, and BLUETTI gives an example of a 1000W generator²⁰. Which? also cautions that because they are small, portable generators have a limited output capacity, and some models will not power all appliances¹⁷.

A practical approach for a power cut is not to try to run the whole house but to choose a few things that matter, as our page on deciding what to keep running explains. A smaller generator may support selected items such as lighting, phone chargers and a refrigerator or freezer¹, which for most households is the actual job. If watts and watt-hours still feel tangled, watts, watt-hours and surge explained unpicks them, and what size generator do I need works through the sizing question.

Rain and weather: most portable generators are not waterproof

Power cuts in the UK often come with the weather that caused them, and that creates a tension: the moment you most need the generator is the moment it is raining. Clarke's guidance is clear: do not use it in rain or standing water¹. A generator should not be exposed directly to rain or standing water, and any suitable protection you rig up must still provide proper ventilation and prevent heat or exhaust gases from building up¹. A canopy or open-sided shelter that keeps rain off while letting air and exhaust move freely can work; a tarp pinned down around a running generator does not, because it traps heat and fumes.

Standing water matters twice over. It is an electrical hazard around a machine producing mains output, and it is a siting problem: position the generator on firm, level ground away from standing water¹. After a flood, generators come into their own for a different reason. London Fire Brigade's after-a-flood guidance notes that if your electricity supply is off or unchecked, you may need a generator to power any pumps, humidifiers, dryers or heaters you decide to use⁸, but the machine still sits outdoors, on ground that is safe and dry.

One planning point for rural households: an Ofgem report on the networks' response to Storm Arwen records Electricity North West's view that some rural locations are unsuitable for large generator installation because of the difficulty of transporting large and heavy equipment in storm conditions²¹. If you live somewhere a lorry struggles to reach in bad weather, your own portable generator, stored ready, may be more reliable than waiting for a large one to arrive. For the detail, see can you run a generator in the rain?.

Servicing and storage: keeping a generator ready to start

A generator that will not start is a very expensive ornament, so the work happens before the power cut, not during it. The Scottish Fire and Rescue Service's heating advice captures the general principle for any fuel-burning equipment: keep it clean and well maintained¹³. For a generator that means following the maker's service schedule for oil, filters and spark plugs, and running it periodically so you know it starts and the output works, rather than discovering a fault in the dark.

Storage is about fuel and damp. Store the generator somewhere dry and ventilated, with fuel and any spare gas cylinders kept outside where possible, and never in a basement, near drains, under the stairs or in a cupboard containing electric meters or equipment¹³. Check the oil and fuel before every use, following the maker's instructions, rather than relying on the engine's own protections. When you set it up again after storage, re-check the siting rules: outdoors, on firm level ground, away from combustible materials, standing water and places where exhaust could accumulate¹.

Think too about how you will move it. Fuel generators are heavy: BLUETTI describes typical fuel generators as weighing 50 to 70kg, noisy and bulky²⁰. Some inverter models ease this with a twin carry handle and an optional wheel kit¹⁸. Decide in daylight where the generator will sit and how it will get there, because you will be doing it in the dark and possibly in the rain. Our pages on how to store a generator after a power cut and backup power checks before winter take this further.

Generators from your network operator during a power cut

Many households assume that if the power is off for days, the electricity network operator will bring a generator. The reality is more limited, and it is worth knowing before you decide whether to buy your own. Operators do use generators, but mainly at network level: Electricity North West explains that generators will sometimes be used for temporarily restoring customers whilst permanent repairs are completed, ordered through network partners who ensure a robust refuelling strategy and connect them safely²². NIE Networks in Northern Ireland says that where possible it fits a generator at the local substation, and it does not fit generators in individual homes or businesses²³.

For individual households, help is targeted at medical need. SSEN's planned power cut guidance states that it only provides generators for customers who are medically dependent on electricity, not for businesses or personal use²⁴. Electricity North West's FAQ says generators are only provided in exceptional circumstances, such as for medical needs like oxygen equipment, mobility aids or end-of-life care, though it adds that in exceptional circumstances such as weddings or funerals it does its best to provide one to minimise the impact of the power cut²⁵. If you rely on your energy supply for medical reasons, your network operator can tell you about planned power cuts, for example when engineering work is scheduled²⁶, so make sure you are on its priority register.

To reach your operator at all, call 105 for free, and you will be put through to your electricity network operator⁴; you can also report an unplanned power cut directly through your local operator's website²⁷. Two smaller points worth knowing: during a power cut, systems like solar panels, heat pumps, EV chargers and batteries automatically switch off to protect your home and engineers working on the network²⁴, and when the repair is finished you may experience a short outage whilst being connected back to the network²². For the wider picture, see power cuts: a household guide.

Choosing between a generator and a battery power station

A generator is not the only way to bridge a power cut, and for some households it is the wrong one. Battery power stations are smaller and more portable than generators that use a fuel tank, but, as Which? puts it, they are only really useful if you have low power demand, though some can be charged with solar panels¹⁷. BLUETTI makes the comparison starkly: where a typical fuel generator weighs 50 to 70kg and is noisy and bulky, a small power station such as the Anker example Which? lists weighs 3.7kg²⁰.

The trade-off is endurance. A fuel generator refills in minutes and runs for hours: BLUETTI's example runs about 6 hours at a 500W load on a 5-litre tank²⁰, and the Briggs & Stratton P2400 inverter runs up to 8 hours at 25% load¹⁸. A battery holds a fixed amount of energy and then needs recharging, from the mains, a car or solar. So the honest summary is this: if your needs are a phone, a radio, some lights and maybe a router for a few hours, a power station is quieter, safer indoors and far easier to live with. If you need to run a fridge and freezer through a multi-day outage, or pumps after a flood⁸, a generator is the tool that does it, provided you can site it safely outdoors. The full side-by-side is in portable power station or petrol generator for a power cut, and the battery options are covered in portable power stations: what they do and how to choose.