Say I want to buy a portable generator, how does one go about calculating the correct size for my requirements?

Add up the usage in (KW) of everything you want to run?

What are you’re requirements? Think my standard 110/240 site genny is 4.5 kva , if I stick the kettle on it it will boil it but it fair makes it grunt!

In my experience, most important consideration with the average genny is a very very very long lead so’s you can site it as far away as possible given that noise attentuation is proprtional to distance

Get a quiet one! Basic generators are cheap, but the noise will do your nut in and those around you! I live on a boat and have a 1000w Kipor generator which is enough for household stuff like computers etc., but not power tools or kettles (anything over about 750w). The best bit is that it is only 59 decibeles and has a built in inverter to deliver the correct sinewave, as well as an intelligent throttle so it only revs to electric demand. It does cost £350, but is well worth it. Had trouble free running so far after a year. Depends what you need it for though, it may be a bit pricey if you use it a few times a year on holiday…

What do you want to power with it?
How long do you want to provide that power?
How often do you want to provide that power?
Where do you want to provide that power?

Start with getting these answered.

I live in the middle of nowhere and power cuts are fairly common. I’d like it to be able to boil the kettle, run the TV/Lights/Computer for a few hours at a time.

I was thinking at Honda 11hp?

Is there still middle of no where left in england ?

Are you planning to hook it up to the house or just run an extension cord out to the genny.

Tbh even when i lived in the realy middle of no where up a glen power cuts were few and far between – the bigger issue was watercuts ……

Also gennys aint the sort of thing you can just trott out at a moments notice – they need looking after and firing up a few times a year otherwise as one of my old clients found out – his genny didn work in the time of need ( and he spent a lot of money getting his professionally fitted to the house so he just flicked the breakers an started it up.

It’ll be the trot out and run an extension cord type of attachment. I’d also like it for events like MM.

Dont use genny to make tea. £15 gas stove and cannisters plus whistle kettle and you are sorted for drink and food.

A 12v airpower charger will run a laptop.

I even have a 12v 19″ TV.

Get a few LED camping lights, they last hours at a time. Or invest in a few 12v lights.

All that and 12v leisure battery with a permanent trickle charger will last hours.

Your kettle will be 2kw most likely, the Honda 11hp is 5kw so you can work out how much your other bits of kit will take and see if the honda will be big enough.

cook on gas, if you must have a generator then buy Honda, and don’t buy it off a pikey.

Our old neighbours in Killin used Honda’s – not sure of output, but it was exactly that reason. One street in the village came from a different supply – over the mountain behind, opposite and through the woods…At least 6-10 blackouts a winter, one being 10 days long once in sub-zero conditions. So it made sense that most people on the street had a wired in genny in the shed and an open fire/woodburner.

You want a 5kW generator for a bike race once a year? Selling hot dogs are we?

For the whole lifetime costs, remember that about 75% of the generator costs are in fuel and maintenance, so you have to budget for that.

It would probbly do you fine, but with a bit of thought and some 12V stuff you could do far more with less power as mentioned by a few people.

I have a crappy 2kW genny I got for building the barn for the 6 months before we had power. Amazingly it turns over 2nd pull even if neglected for a year.

Although we use wood fuel for heating and hot water, I still need to power 3 or 4 standard CH pumps to get the hot water from the wood boiler to the radiators or UFH. That’s around 200W.

I have a 300W inverter in the camper van and around 160Ah of batteries available to run it off. Assuming I can use say 50% of the batteries before they’re kackered/losses that means I can run the pumps for 160*50%*12v/200W = 5hrs.
Which isnt going to do a lot 🙂

And Im not running the genny to do 300W.

SO my zombiepocalypse plan is to make the mattresses up in front of the wood stove. Cook and boil water on the stove top. And use the batteries to charge the phones so that I can get on STW. And make a big pot of baked beans.

The small whisperlite Honda things are really pretty quiet and run all day, you see loads of them in use for market stalls etc, often with a wooden cover over them. I keep meaning to get one so I can power the boiler and CH pump in case we get a black out, but they’re not cheap.

If you’re running stuff like a computer don’t you want one with a voltage regulator built in, which most of the cheap petrol ones don’t have? Admittedly I’ve done it several times before but I’ve been warned not to!

Careful with cheap generators as they do not give a nice clean supply. You will get voltages well out side what is allowed for your DNO to supply you as well as varying frequencies. Boil a kettle ok. Run that expensive home entertainment system NO.