Your generator
Tell us about your generator and it stops being guesswork. We work out when you would actually start it, how long you would leave it running, and what that costs you in petrol. You get it day by day, month by month, and across a whole year.
What we ask you, and what each answer changes
- How big is it? A common 3 kW petrol generator suits most homes and is easy to buy. Around 2 kW is caravan sized. Serious off-grid homes often run 5 kW to 10 kW. This makes more difference than anything else to how long it has to run.
- How far does a litre go? A small petrol generator gets you roughly 1.5 units of power per litre with its eco setting on. Diesel does better, around double that. ⚠️ Every litre and dollar we quote rests on this number, so it is the one worth checking against your own jerry can.
- What does fuel cost you? What you actually pay at the pump. Leave it and we use our own figure, and we say so rather than pretending it was yours.
- When is it allowed to run? Neighbours, council noise rules, or just not wanting to be woken at 3am. ⚠️ Leaving this empty means it can run at any hour, not that it never runs.
- What is the shortest run worth bothering with? Nobody starts a generator for four minutes. Once it is going we keep it going for at least this long, which is part of why the fuel figure is sometimes higher than you would guess.
Why it burns more than you would expect
A generator burns fuel for what it is making, not for what your house happens to be using. Run a 3 kW generator for an hour while the house only wants half that, and you have burnt a full hour of petrol for half the benefit. The rest goes into the battery if there is room, and is simply lost if there is not.
So we count every hour it runs as a full hour of fuel. It is the gloomier way to add it up and it is the honest one, because it matches what you actually end up pouring in. Working backwards from the power your house used would look neater on screen and leave you short at the servo.
It also means a big generator gets started less often rather than run gently. That is right. A big engine ticking over into a battery that cannot take the power is wasting fuel, and your plan should show that rather than hide it.
“I set up a generator and nothing changed”
If you are still connected to the grid, that is what should happen. Your normal forecasts assume you have mains power, so a generator has nothing to do. It only shows up in the Off-grid tab, as a what-if.
To make the generator part of your real plan, use the Off-grid tab to set your place up as an off-grid one. There is no mains power there, so the generator is part of every answer.
Where to change it later
Open your layout and click the pencil on the Generator row, or use the change link in the box at the top of the Off-grid tab. If you have set a generator up while still on the grid, that row stays visible so you can always get back to it.
Closes this tab and returns to the calculator.