Storing generator fuel safely

A generator is only as useful as its fuel. During regional outages gas stations may be closed, so many households store fuel ahead of time. That fuel must be stored safely and kept fresh.

Gasoline storage basics

• Use only containers made and labeled for gasoline. Keep caps tight.
• Store fuel outside the living area, in a detached shed or a well-ventilated garage away from water heaters, furnaces, and other ignition sources. Follow local fire codes, which often limit the amount you can keep.
• Keep containers out of direct sun and away from children.
• Never store gasoline in the house or basement.

NFPA advises storing generator fuel in approved containers and away from fuel-burning appliances.

Keeping gasoline fresh

Gasoline breaks down over time. It can leave gum and varnish in a carburetor, which is a common reason a generator that sat all year will not start. Two habits help:

1. Add fuel stabilizer when you fill the storage can, following the product label.
2. Rotate the fuel. Pour stored gas into your car and refill the can with fresh gas on a regular schedule.

Many generator manuals also recommend running the carburetor dry or draining it for long storage. Check your manual; procedures differ.

Propane and dual-fuel generators

Dual-fuel generators can run on propane, which does not go stale. Standard barbecue-size cylinders are easy to swap, and larger cylinders or a permanently installed tank extend run time. Propane contains less energy per gallon than gasoline, so a generator usually produces somewhat less power and burns more fuel volume on propane; check your model’s propane ratings. Store cylinders outdoors, upright, and never indoors or in a garage.

How much should you store?

It depends on your generator, your load, and how many hours a day you run it. Our fuel run-time estimator starts from your generator’s spec-sheet run time and your planned hours. Ready.gov suggests planning for outages lasting several days.

Refueling safely

The CPSC and NFPA both say to turn the generator off and let it cool before refueling. Gasoline spilled on a hot muffler can ignite. Refuel outdoors, wipe up spills, and move the fuel can away before restarting.

Quick rules

• Approved cans, outside the living space, away from ignition sources.
• Stabilizer plus rotation.
• Engine off and cool before refueling.
• Check local limits on how much fuel you may store.

How much fuel does a generator actually use?

Fuel planning starts with consumption. Manufacturers usually publish runtime at 25% or 50% load on a full tank. Divide tank size by runtime to get gallons per hour. As a rough illustration:

• A small 2,000 to 2,500-watt inverter generator at a light load may use roughly 0.1 to 0.15 gallons of gasoline per hour.
• A 7,000 to 9,500-watt open-frame generator at half load commonly uses roughly 0.6 to 0.8 gallons per hour.

Those differences add up fast. Over 24 hours, the small inverter might use 3 gallons while the large unit burns 15 or more. Check your own spec sheet, then multiply by the hours per day you expect to run. If you'll use load management and run the generator, say, 12 hours a day instead of 24, your fuel needs drop by half. See how long can a generator run.

Why propane goes farther in storage but not per gallon

Propane doesn't go stale the way gasoline does, which makes it attractive for long-term storage. But a gallon of propane holds less energy. The U.S. Energy Information Administration lists about 120,214 Btu per gallon for gasoline and about 91,452 Btu per gallon for propane. So a generator burning propane uses more gallons for the same work, and dual-fuel models usually produce somewhat less power on propane. A standard 20-pound grill cylinder holds about 4.7 gallons of propane when full. Plan your cylinder count from the generator's propane runtime rating, not its gasoline rating. Our propane vs. gasoline guide works through the math.

Rotating gasoline so it never goes stale

The simplest way to keep stored gasoline fresh is to keep using it:

1. Label each can with the purchase date.
2. Add fuel stabilizer when you fill the can, following the product's label.
3. Every few months, pour the oldest can into your car or lawn equipment, then refill it with fresh fuel and stabilizer.
4. Before storm season, top up all cans.

This "first in, first out" rotation means your emergency supply is never more than a few months old, without needing special long-life fuel.

Where to store fuel

• Outside the living space. A detached shed or garage is better than an attached garage, and never in a basement or near a fuel-burning appliance, water heater, or furnace.
• Away from ignition sources and out of direct sun.
• In approved containers with intact caps and spouts.
• Out of reach of children.
• Within local limits. Many local fire codes limit how much gasoline you can store at a home. Check with your fire department.

Propane cylinders should be stored upright, outdoors, and never indoors or in a garage, with the valve closed and the plastic protective cap on when they're disconnected.

Refueling during an outage

Ready.gov advises letting the generator cool before refueling, because fuel spilled on hot engine parts can ignite. Practical habits:

• Shut the generator off, wait for it to cool, and refuel in daylight if you can.
• Use a funnel or a spout with automatic shut-off to avoid spills.
• Wipe up spills and let vapors clear before restarting.
• Never refuel indoors or in a garage.
• Keep a fire extinguisher rated for flammable liquids near your fuel storage area.

When fuel goes bad

Signs of stale gasoline include a sour or varnish-like smell, darker color, and hard starting, surging, or stalling. If you suspect bad fuel, drain the tank and carburetor according to the owner's manual, and dispose of the old fuel at a household hazardous waste site. Most local waste agencies accept it. Don't pour it on the ground or down a drain.