Off-Grid · Power · Generators
Generators: The Honest Winter Backup
Nobody puts the generator on the brochure, but nearly every real off-grid home has one — and is very glad of it about three weeks a year. It's the insurance that lets you size thesolar and batterysensibly instead of paying for a monster array to cover the darkest fortnight. Used right, it runs a handful of hours a winter and earns its keep every time.
The generator isn't there to run your house — it's there to top up the batteryon the black days when the panels can't. Understand that one job and everything about choosing and wiring it gets simple.
A generator charges the battery; it doesn't power the house directly. You run it for a few hours, it pushes charge into the bank through your inverter/charger, and then it goes off again while the battery quietly runs the home. That's why a fairly small, efficient generator does the job — you're filling a battery, not carrying every load in the house at once.
How the generator fits with the panels, battery and inverter — the whole system.
Read the hub →🔌 Inverter/chargerThe box the generator charges through — sizing, pure sine, and the generator input.
Read the guide →🌬️ Wind turbinesThe other winter backup people reach for — and why it's usually the wrong buy inland.
Read the guide →Inverter or conventional? inverter, for a home
Inverter generators — quiet, thrifty, clean power
A modern inverter generator throttles its engine to the load, so it's far quieter, sips fuel, and puts out clean, stable power that battery chargers and electronics like. For an off-grid home that runs it occasionally to charge the bank, this is the right type — you'll bless the quiet on a dark evening.
Conventional open-frame — cheap, loud, thirsty
The big open-frame builder's generator is cheaper to buy and fine for running power tools on the job, but it's noisy, drinks fuel, and its power is rougher. As a battery charger for a home you'll live next to, the inverter type is worth the extra.
Petrol, diesel or dual-fuel? depends on your setup
Petrol — cheapest to buy, easiest to live with
Most small inverter generators are petrol. They're the cheapest up front, light, and quiet. The downsides: petrol doesn't store as long, and you're carrying cans. For occasional winter charging, a good petrol inverter unit is the common, sensible choice.
Diesel — dearer, but it fits an off-grid fuel plan
Diesel generators cost more and can be noisier, but diesel stores better, and if you already keep diesel for a vehicle or heater it can simplify life to have one fuel. On a bigger system diesel starts to make sense; on a small one the price premium often isn't worth it.
Dual-fuel (petrol/LPG) — worth a look
A dual-fuel generator that also runs on LPG is handy: bottled gas stores indefinitely and burns cleanly, so it's a good "sits in the barn for emergencies" fuel alongside petrol for regular use. A nice flexibility if the budget allows.
Sizing and wiring it in
Size it to your charger, not your house
Because it's feeding the battery, match the generator to how fast your inverter/charger can push charge in — typically a modest few kW is plenty for a home bank. A giant generator just wastes fuel idling. Small, efficient, matched to the charger: that's the brief.
Wire it through the inverter/charger
The clean way: the generator's output goes into your hybrid inverter/charger, which uses it to charge the battery (and can pass power through to the house meanwhile). You start the generator, the charger does the rest, you stop it when the bank's full. Don't cobble the generator straight onto house circuits — let the charger manage it.
Site it for noise, fumes and fuel
Put it away from the bedroom window, never run it indoors or in a closed space (carbon monoxide kills), keep fuel stored safely and legally, and do the basic servicing — oil, filter, the odd run to keep it healthy. A generator you look after starts first pull on the cold morning you need it.
What it costs
Buy-once ranges, plus the fuel you'll actually burn — which off-grid is surprisingly little.
- £300–700A decent portable petrol inverter generator — the common off-grid backup, ample to charge a home bank.
- £700–2kA larger, quieter or dual-fuel/diesel unit — for bigger systems or if you want to run it less often, harder.
- £ small/yrFuel: run only in black spells to charge the battery, most homes burn very little across a winter — a few tanks, not a livelihood.
Power is one system of four
The generator, panels and battery are the electric half; water, waste and a warm room complete the build. See the whole thing in order.
The whole off-grid build →