How to Prepare a Generator for Storage: Steps for Months of Idle

Why storage preparation matters

A generator that sits idle for months without preparation can become hard to start or refuse to start altogether. Fuel degrades, carburetor jets gum up, and battery charge fades. The goal of long-term storage is to keep the engine ready for the next emergency. Taking an hour after your last use prevents a frustrating, sometimes costly repair later.

Portable generators are often used for backup power during outages and then remain untouched for months. Whether you own a small inverter model or a large dual-fuel unit, the storage steps are similar. They involve the fuel system, the lubrication system, and the electrical system. Each one matters. If you are choosing a generator with storage in mind, compare models in our best portable generators guide.

Fuel system: stabilize or drain

The most important step is dealing with the fuel. Gasoline begins to degrade within weeks. As it breaks down, it leaves a sticky varnish inside the carburetor and fuel lines, which clogs the tiny passages. You have two good options: add a fuel stabilizer and run the engine, or drain the fuel system completely.

If you use a stabilizer, follow the product's instructions for the correct amount. Add it to the fuel tank, then run the generator for a few minutes so the treated fuel reaches the carburetor. If you prefer to drain, turn off the fuel valve and let the engine run until it stops from lack of fuel. Then empty the carburetor bowl if your model has a drain screw. This removes all gasoline from the system.

Draining is the most thorough approach. A completely dry carburetor cannot gum up. Always consult your generator's manual for the exact procedure, because the location of the fuel valve and drain screw varies. For guidance on fuel quality and additives, see our article on fuel stabilizer and storage life.

Change the oil before storage

Old oil contains combustion byproducts, acids, and moisture that can eat at engine bearings and cylinder walls over months. A fresh oil change before storage gives the engine a clean, protective coating. Run the engine for a few minutes first to warm the oil, which makes it flow out faster and carries more contaminants with it.

Then change the oil according to your generator's manual. Replace the oil filter if your model has one. This is also a good time to check the air filter. A clean filter prevents dust from entering the engine while it sits. For details on oil types and intervals, see our guide on generator oil change interval or our article about oil types and viscosity.

Battery care and maintenance

If your generator has electric start, the battery deserves attention. A lead-acid battery slowly discharges on its own. Over months, it can drop below a healthy voltage, which shortens its service life. A discharged battery in freezing temperatures can also crack.

The simplest method is to disconnect the battery and store it in a cool, dry place. Even then, recharge it every few months. A battery maintainer, sometimes called a trickle charger, is even better: it keeps the battery at the optimal state without overcharging. Leave it connected and the battery stays ready for the next season. Some generators have a battery disconnect switch, which makes this easy. For more on the electrical system, see our article about generator electric start battery.

Cover and choose the right location

Where you keep the generator matters as much as what you do to the engine. A dry, clean space prevents rust and corrosion. A garage, shed, or basement works, as long as it does not have high humidity. Avoid storing it directly on a bare concrete floor because moisture can seep up into the frame. Place it on a wooden pallet or a rubber mat.

Cover the generator with a breathable fabric cover. A fitted generator cover keeps off dust, dirt, and splashes. A plastic tarp traps moisture underneath, which can defeat its purpose. Make sure the cover does not trap humidity against the exhaust or the control panel. Before you store, clean any dirt or grease from the unit. A shiny generator is easier to inspect before the next use.

Seasonal checks and exercise runs

Long-term storage is not 'set it and forget it.' Check the generator every month or two. Look for rodent nests, corroded terminals, or fuel leaks. If you stored it with fuel in the tank, verify the fuel level and condition. Condensation can form in a partially full tank over months, so topping it off before storage helps prevent water buildup.

Run the generator for about half an hour once every month or two under a light load. This keeps the engine lubricated, the seals fresh, and the battery charged if it stays connected. The exercise run also confirms the generator will start when you need it. Our guide on generator exercise schedule explains the practice in more detail. If you notice any issue during the run, address it before it becomes a breakdown.

• Inspect for leaks, rust, or pests monthly.
• Recharge or check the battery every 4 to 6 weeks.
• Run the generator briefly to keep seals and engine lubricated.
• Monitor the fuel condition if the tank was not drained.

Steps when taking it out of storage

When the power goes out, you need the generator to start immediately. Before that moment, you should have already verified it. When you bring the generator out of storage, check the oil level, confirm the fuel system is clean, and inspect the air filter. If the battery was disconnected, reconnect it and charge it fully if you did not use a maintainer.

Start the generator outdoors, well away from your home. Carbon monoxide from a generator can kill you in minutes, so use it outdoors only, at least 20 feet from windows, doors, and vents, as advised by the CDC. Never run it inside a garage, even with the door open. Install battery-operated CO alarms in your home to protect your family. Many modern generators have built-in CO detection, which adds another layer of safety. For more on this topic, read our article on what is a CO sensor on a generator.

What to pick for your use

Questions

How long can a generator sit unused without damage?

Its depends on how you prepare it. Untreated gasoline can degrade in as little as a few weeks. If you drain the fuel system and change the oil, a generator can sit safely for many months. Without preparation, you may face a clogged carburetor and hard starting when you need it.

Should I run my generator before storing it?

Yes, run it for a few minutes after adding fuel stabilizer so the treated fuel reaches the carburetor. Also run it to warm the oil before an oil change. If your storage plan is to drain the fuel, run the engine until it stops from lack of fuel to empty the carburetor.

Is it better to drain the carburetor or leave fuel in it?

Draining is better for long-term storage. A dry carburetor cannot form varnish. Leaving fuel with a stabilizer works for a few months, but even stabilized fuel eventually breaks down. Check your owner's manual for the correct drain procedure.

Can I store my generator in a garage or shed?

Yes, a dry, clean garage or shed is fine for storage. Never run the generator indoors, in a garage, or in a shed, even for a quick test. Carbon monoxide accumulates quickly. Always start it outdoors at least 20 feet from windows, doors, and vents.

How often should I start a stored generator?

Run it once every one or two months under a light load. This keeps the engine lubricated, circulates the oil, and recharges the battery if it is still connected. It also confirms the generator still starts, so you can fix issues before an outage.

Do I need to disconnect the battery for storage?

Disconnecting prevents slow discharge and protects the battery. A battery maintainer is even better, as it keeps the charge level optimal. If you do not disconnect, check the battery voltage periodically and recharge before it drops too low.

Why does stale fuel cause starting problems?

Gasoline degrades, leaving sticky gum deposits inside the carburetor and fuel passages. These deposits clog the tiny jets and prevent the correct fuel-air mix. Draining the fuel system before storage avoids this issue entirely.