What Size Generator Do I Need? Tools, Laptops and Power Cuts

Whether the power is off at home or there is no supply on site, generator sizes can be baffling.

Start by matching the continuous rating to everything you will run at once. PartsForMachines lists over 50 SIP, Draper, Sealey, Clarke and EcoFlow generators in its generators range, from small inverters to silenced diesels.

What Size Generator Do I Need?

Add up the running watts of everything you will use at the same time, then choose a generator whose continuous output covers that total. Use the continuous (rated) figure, not the maximum: the G2201 petrol generator gives 2kW continuous and 2.2kW maximum. The number in a model's name can be the maximum, so check: the G2000I is rated 1.6kW continuous.

Allow for start-up surge as well. Motors in fridges, compressors, pumps and power tools can draw several times their running power for a few seconds as they start. Add the biggest starting load on top of everything else that is running, and take each wattage from the appliance's rating plate.

Will a Generator Damage My Laptop or TV?

Not if it gives clean, stable power. Inverter generators produce cleaner, steadier power with lower harmonic distortion, which suits laptops and other sensitive electronics, and some slow the engine at light load to save fuel and noise. On a conventional generator, look for an automatic voltage regulator (AVR), which keeps the voltage steady; some AVR models are rated for laptops and televisions.

Open frame describes the build, not the electronics. The 95204 open-frame inverter generator pairs pure sine wave output, suited to laptops and TVs, with a steel tubular frame, and is rated at 2.8kW.

Can a Generator Run My House in a Power Cut?

It can keep the essentials going, such as a fridge freezer, lamps and a laptop, if you plug them straight into the generator's own sockets with heavy-duty extension leads. Size it as above, allowing for the fridge's start-up surge, and run it outdoors.

Never plug a generator into a socket in the house. Power can feed back through the wiring into the network and put anyone working on the lines at risk. Powering anything wired in, such as a boiler, is a job for a qualified electrician.

How Quiet Is a Quiet Generator?

Some small inverters are rated below 60dB(A) at 7 metres, but only compare figures measured the same way. Sound pressure falls as you move away from the machine, so a figure taken at source reads far higher: the G2201, for example, carries 94dB(A) at source and 76dB at 7m.

For quiet running, the ISG2202 digital inverter generator is rated at 58dB(A) at 7m. A 10dB rise sounds roughly twice as loud, so small gaps on paper still matter.

What Should I Check Before I Buy?

• Continuous output against everything you will run at once, plus the biggest start-up surge.
• A pure sine wave inverter or an AVR if you will power electronics.
• Sockets and ratings: 230V or 110V, 16A or 32A, 400V three phase or 12V DC.
• Run time at your likely load, tank size and fuel: petrol or diesel.
• How the noise figure was measured, plus weight, wheels and electric start.

Not sure what you need? Contact the PartsForMachines team by WhatsApp, telephone or email with a list of what you want to power, or browse the generators range.

Product options, delivery options and returns terms are shown on each product page. A 30-day return policy applies to eligible items.

Frequently Asked Questions

Should I compare kVA or kW?

Compare kW, because you add up your appliances in watts. Some generators quote both: the 95204, for example, is rated 2.8kW (3.5kVA). If a rating plate shows only amps, ask our team to help work it out.

Will a generator run my welder?

Only if it covers the welder's input rating plus other loads. For stick welding off the mains, the P200W-AC ES welder generator gives 60A to 200A for 1.6mm to 5mm electrodes, with up to 7kVA of site power as well. Welding leads are sold separately.

Should I choose petrol or diesel?

It often comes down to portability against long running. Petrol covers the light, portable end, such as the 20kg ISG2202. Our four diesels weigh 141kg to 291kg; the DG7000 gives 6.5kW continuous, and its 23-litre tank runs for up to 9 hours.

How long will a generator run on a tank of fuel?

It depends on the load as much as the tank. The ISG2202 runs 3.5 hours at full load but 8 hours at a quarter load. The T5500 silenced diesel runs 7.5 hours at full load and 15 hours at half load.

Do I need 110V sockets on a building site?

Only if your site tools run on 110V. Dual-voltage models cover site-voltage and standard tools, such as the MGHP3.5FF generator with one 230V 16A and one 110V 16A socket. Some larger units add 32A sockets.

Can I run a generator in a garage or shed?

No. Generator exhaust contains carbon monoxide, which you cannot see or smell and which can kill. Never run one indoors, in a garage or in a shed, even with the door open; keep it outdoors, well away from doors, windows and vents.

Can a generator charge a battery power station?

Yes, with the right kit. The DELTAPROTG adapter links an EcoFlow Delta Pro power station to an EcoFlow Smart Generator for automatic pass-through charging. For larger off-grid or backup systems, the Power Hub 5kVA works with 48V LFP battery systems and can expand to 45kWh.

Can I service a generator myself?

Routine servicing, yes, following the checks and schedule in the manual. The 2.8kW open-frame inverter above, for example, takes 0.6 litres of SAE 10W-30 oil. For the T5500 silenced diesel, the PW01-03143 service kit holds the fuel filter, oil filter and air cleaner element.

Can a generator take over when the mains fails?

Some are built for standby use. The T15000 silenced diesel has an automatic transfer switch that keeps the supply running when the mains drops. SIP calls for a site survey self-assessment first, and connection to any building's supply is a job for a qualified electrician.