How to Store a Generator Between Outages

1. Why Stored Generators Fail

Every row is preventable, and every prevention takes minutes rather than hours. The first row alone accounts for the large majority of generator no-starts, and it comes down entirely to what was left in the tank.

It is worth being blunt about the stakes. A generator that does not start during an outage is not an inconvenience to sort out later — it is the specific failure the machine exists to prevent, occurring at the only moment it matters. Fifteen minutes a month is a small premium against that.

2. Pick a Fuel Strategy and Commit to It

There are two valid approaches. The failure mode is the third option that most people default to without deciding: half a tank of untreated fuel, left alone.

Option A: Full and Stabilised

Fill the tank, add fuel stabiliser at the labelled dose, then run the engine for ten minutes so the treated fuel reaches and fills the carburetor. This matters — stabiliser sitting in the tank does nothing for the carburetor bowl, which is where varnish actually forms.

A full tank also minimises the air space where condensation forms, which is why this approach suits unheated storage where temperatures swing. Expect to refresh the fuel every six months or so, and rotate the old fuel into a car rather than leaving it.

Option B: Completely Dry

Close the fuel valve with the engine running and let it run until it stops on its own, which empties the carburetor bowl. Then drain the tank, or run the tank down first and finish with the valve. Some carburetors have a bowl drain screw worth using as well.

With nothing in the system there is nothing to go stale, which makes this the more robust option for a machine that will genuinely sit untouched. The trade is that you need fuel on hand to deploy it, and pouring fuel into a dry generator in the dark during a storm is a real inconvenience.

If your generator runs on propane as well as petrol, use propane for the monthly exercise runs. It burns clean, leaves no varnish whatsoever, and means the carburetor stays pristine in a machine that mostly sits still. That single habit is the strongest practical argument for dual fuel, covered in our dual fuel testing.

3. Shutting It Down After an Outage

The end of an outage is when everyone is most tired and least inclined to do this properly, which is exactly why it is worth having a routine.

Let it cool before touching fuel. Never drain or fill a hot engine. Give it at least fifteen to twenty minutes.

Change the oil if it ran hard. A generator that worked through a multi-day outage has done more hours than it usually sees in a year. Used oil holds acidic combustion by-products that attack bearing surfaces while the machine sits, so changing it before storage rather than before the next use is the right order. These engines hold about a quart, so it is a five-minute job.

Clean it down. Wipe fuel and oil off the housing, brush debris out of the cooling fins and air intake, and check the air filter — an outage often means dust, leaves and rain. A dirty filter that sits for a year is a filter that restricts airflow next time.

Then apply your fuel strategy from the section above, coil the cords properly rather than dumping them, and note the hour meter reading somewhere you will find it.

4. The Monthly Exercise Run

This is the single highest-value habit in generator ownership, and it takes half an hour a month.

Run the machine for twenty to thirty minutes with a genuine load connected — a space heater, a couple of work lights, a shop vacuum. Loading it matters because it brings the engine to full operating temperature, which burns off moisture in the crankcase and exhaust, and because it exercises the alternator rather than just spinning it.

Three things happen that you cannot get any other way. Fresh fuel moves through the carburetor, preventing deposits from establishing. The alternator's residual magnetism is maintained, which prevents the frustrating fault where a generator runs perfectly but produces no output — covered in why a generator runs but produces no power. And you find out about problems in your own time rather than during a storm.

Put it in the calendar on a fixed day — the first Saturday of the month works for most people. Every owner intends to do this; the ones who actually do it are the ones who scheduled it. Observe the same safety rules as always: outdoors, twenty feet from any window, door or vent, exhaust pointed away from the house.

5. Battery and Electrics

If your generator has electric start, the battery is the second most likely thing to let you down after the carburetor. Small starting batteries self-discharge steadily over months, and their cranking capacity drops sharply in cold — so a battery that turned the engine over easily in October may not manage it in January.

A trickle charger or battery maintainer costs around $30 and solves this completely. Leave it connected through the storage season if there is power where the machine lives, or bring the battery indoors and maintain it there. Check the terminals for corrosion while you are at it and clean them if needed.

Also test the recoil starter, even on an electric-start machine, and especially if you have never pulled it. It is the backup for the exact failure you are trying to prevent, and a recoil spring that has seized in storage is worth discovering on a calm afternoon rather than in a blackout.

Finally, look after the cords. Coil them loosely rather than tightly around the frame, keep them off a concrete floor where moisture wicks in, and inspect the plugs and outlets for corrosion during the pre-season check. A generator with a corroded outlet is a generator you cannot safely connect anything to.

6. Where to Keep It

• Dry and ventilated beats warm. A garage or shed is ideal. Unheated is fine; damp is not, because moisture in the alternator windings causes start-up problems.
• Off the floor. A pallet or a couple of timbers stops moisture wicking up from a concrete slab and keeps the machine clear of any water that gets in.
• A breathable cover, not a tarp. Plastic sheeting traps condensation against the machine. A purpose-made generator cover lets moisture out while keeping dust off.
• Somewhere you can actually get it out of. A machine behind the bikes, the mower and four boxes is a machine that gets deployed late, if at all.
• Fuel stored separately. Cans belong in a detached shed or garage, never in the house, in approved containers, dated and rotated.
• Consider security. Generators are stolen frequently, and most in the days after a regional outage. A cable lock through the frame is worth the ten dollars.

Keep a small box beside it with the things you will otherwise hunt for in the dark: two heavy-gauge outdoor extension cords, a funnel, a head torch with fresh batteries, a quart of the correct oil, a spare spark plug and the manual. Assembling that once turns deployment into a five-minute job.

7. The Pre-Season Check

Once a year, in early autumn before the weather turns, go through the machine properly rather than just running it.

Change the oil if it is due or if it looks dark. Inspect and clean or replace the air filter. Pull the spark plug, check it for fouling, clean or replace it and confirm the gap. Look over the fuel line and any propane hose for cracking or hardening. Check the recoil pulls smoothly and the electric start turns over strongly. Inspect every outlet and the cords for damage or corrosion.

Then run it under load for a good half hour and confirm the output — plug something in and check it actually works, rather than assuming. If you have a transfer switch, test the whole chain from generator to panel, because a switch that has sat for a year is another thing that can surprise you.

Do this in September rather than when a storm is forecast. Parts are available, dealers are not busy, and you have time to fix whatever you find. A generator checked in the calm is a generator you can rely on in the storm, which is the entire point of owning one.