How to choose a generator: power, inverters and what nobody tells you

Every winter, when the tramontana (the strong north wind) leaves farmhouses and urbanisations without power, customers come in looking for "a generator" the way you would buy a torch. And every summer, the day after a party or a fair, one comes back because "it won't pull". The difference is always the same: knowing how much power you really need, and what for.

First: what are you plugging into it?

Make the list and add up the watts (it is on the label of every appliance). But watch out for two traps:

• Anything with a motor (fridge, freezer, water pump, compressor, table saw) draws up to three times its rated power for a moment on start-up. A 200 W fridge can ask for 600 W as it kicks in.
• Anything with a heating element (water heater, oven, iron) draws exactly what it says, but without let-up: a 2,000 W heater is 2,000 W the whole time.

Add up the loads, apply the start-up surge to the biggest motor, and add 20-25% headroom. A generator permanently working at its limit lasts half as long.

Inverter or conventional

Inverter generators produce clean, stable current, just like the mains. They are the ones for anything with electronics in it: computers, televisions, gas boilers, modern fridges, chargers. They also match engine speed to demand, so they use less fuel and are far quieter. The Honda EU22i, 2.2 kVA, is the model we recommend most for a house during a power cut, or for a campervan.

Conventional ones (with an AVR regulator) give you more power for less money and are perfect for building sites, water pumps, power tools and motors — anywhere the quality of the current is not critical. We stock ANOVA and Honda, from 2 to over 10 kVA.

Petrol, diesel, single-phase or three-phase

• Petrol for occasional use and up to 7-8 kVA: cheaper, lighter and quieter.
• Diesel for long hours at a stretch, building work or irrigation: dearer, but they use less fuel and will run all day.
• Three-phase only if you have three-phase machinery (big pumps, sawmills). For a house or a small workshop, single-phase.

The mistakes we see most

• Running it indoors or in the garage with the door shut. Carbon monoxide gives you no warning. Always outside, well away from windows.
• Wiring it into the house consumer unit with an improvised cable. If you want to feed the whole installation, you need a changeover switch fitted by an electrician; otherwise, plug the appliances straight into the generator.
• Stale petrol: a generator that has sat for eight months with a full tank will not start when you need it. Drain it or add stabiliser, and run it for a quarter of an hour once a month.
• Forgetting the oil: the first change is at 20 hours and after that every 50-100. Many models have a low-level alarm that shuts the engine down: if it "cuts out on its own", that is often why.

For a house in the Empordà

To ride out a power cut with the fridge, lights, router, boiler and a couple of sockets, 2 to 3 kVA of inverter is all you need, and it fits in a car boot. If you also have to run the well pump or the pool filter, now we are talking 5 kVA and a conventional machine.

Bring us the list of what you want to run and we will tell you which generator suits you, without selling you power you will never use. Call us or come into the shop: we have them on display and we hand them over with oil in, tested and explained.