Propane vs. Gas Generators: Which Is Better for Emergencies?
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Quick answer: for emergency backup, a dual-fuel generator that runs on both propane and gasoline is the most flexible choice. Propane stores for years without going bad, which makes starting more reliable after long storage, while gasoline is easier to find and gives slightly more power. Whichever you choose, run it outdoors at least 20 feet from the house and install battery-powered carbon monoxide alarms.
Choosing between a propane and a gasoline portable generator comes down to fuel storage, availability, power output and your own habits. Both are useful, and both can kill if used indoors. This guide compares the two on the points that matter for emergency use, and begins with the safety rules that apply to every generator.
First, generator safety
Carbon monoxide from generators kills people every year. The CDC and CPSC say to never use a generator inside a home, garage, basement, crawlspace or shed, even with doors and windows open, and to place it outside at least 20 feet from windows, doors and vents with the exhaust pointed away. Do not run it on a porch or in a carport. Keep it dry, let it cool before refueling and use heavy-duty extension cords. Do not connect it to your house wiring without a licensed electrician installing a transfer switch. The CPSC recommends models with a carbon monoxide shut-off feature and battery-powered CO alarms on every level.
What is a portable generator?
A portable generator is an engine-driven machine that converts fuel to electricity, usually through outlets you plug appliances into. Models vary from small inverter units that can run a few lights and a phone charger to larger frame units that can power a refrigerator and a furnace fan. Always add up the wattage of what you want to run, including the higher starting wattage for motors, and pick a generator with enough capacity and some margin.
Main differences: propane vs. gasoline
- Fuel storage: propane does not degrade in a sealed tank, while gasoline does.
- Availability: gasoline is sold at many stations but may be hard to get in a widespread outage; propane cylinders are sold at many stores and can be stored in advance.
- Output: gasoline generally gives slightly more power; propane output is usually somewhat lower, so check the generator’s rated watts on each fuel.
- Cleaner burning: propane tends to leave less residue in the engine, which helps with long-term reliability.
- Dual-fuel models can run on either.
Factors to consider
Fuel type and shelf life
Untreated gasoline can start to degrade within a few months. Ethanol in most pump gasoline attracts moisture and can separate, which makes engines run poorly or not at all. Sources vary, but a common planning figure is three to six months untreated and about a year with a quality stabilizer, with some manufacturers claiming longer. Always follow the stabilizer’s instructions and rotate your fuel. Propane does not degrade in a sealed, undamaged tank. The cylinder is the limit, and portable DOT cylinders generally need requalification after a set period, so check the date stamped on the tank. See our guide to storing gas long term.
Availability in an emergency
During a storm or widespread outage, gas stations may be closed or unable to pump without power. Having propane cylinders on hand means you do not depend on a station. Keep in mind that propane cylinders must be stored outdoors in an upright position away from heat and ignition sources, never in the house or an attached garage.
How much fuel you need
A typical 20-pound cylinder holds about 4.7 gallons of propane, filled to roughly 80 percent. How long a cylinder runs depends on the generator and its load. Our guide to how long a generator runs on a 20 lb propane tank shows how to estimate it. Plan more fuel than you think you need.
Efficiency and cost
Fuel prices and consumption vary, so compare real numbers where you live. Gasoline is often cheaper per unit of energy at the pump, but you must buy stabilizer and rotate it. Propane costs more per hour of use in many areas, but it keeps. Inverter generators use less fuel at light loads than conventional models.
Generator lifetime and maintenance
Engines last longer when they are run regularly and fed clean fuel. Gasoline leaves varnish in the carburetor if fuel sits, which is a common reason stored generators will not start. Propane avoids that problem. Whatever you choose, start it and run it under load every month or two, change the oil on schedule and follow the manual. Our guide on starting a generator that has been sitting helps if yours has been idle.
Noise
Noise depends on the design more than the fuel. Inverter models are usually quieter than conventional open-frame units. Check the decibel rating, and think about neighbors.
Cold starts
Gasoline engines can start harder in the cold, and propane vaporizes poorly in very low temperatures. Check the manufacturer’s guidance for cold-weather operation, and keep cylinders upright and sheltered from the worst cold, though never in an enclosed space. Our guide to the portable generator exhaust temperature feature explains one safety feature to look for.
Storm season notes
Before storm season, test your generator, stock fuel and check your extension cords, CO alarms and power strips. Place the generator on a dry, level surface outdoors, away from the house, and use a canopy designed for generators if needed, but never put a generator in any enclosed structure. Never refuel while it is running or hot. Keep a fire extinguisher nearby, and tell your family where the generator is and how to shut it off.
Reasons you might not want propane
- Runtime: a small cylinder runs a generator for a limited time, so a long outage needs many cylinders or a larger tank.
- Lower output: you may get less power than on gasoline.
- Cost per hour: propane can cost more to run, depending on your area.
So which should you choose?
For most households, a dual-fuel generator offers the best of both: gasoline when it is available and propane for reliable long-term storage. If you only want one, choose propane if you value dependable starts after long storage and are willing to buy extra cylinders, or gasoline if you can rotate fuel and want maximum output for the price. Earlier versions of this article named the Westinghouse WGen9500DF and Durostar DS4850EH dual-fuel models; we have not re-verified their specifications or safety features, so check the manufacturer details, wattage ratings and CO shut-off protection before you buy. For winter planning, read our guide to preparing for a winter power outage.
Quick buying checklist
- Add up the running and starting watts of what you need to power, and choose a generator with a margin above that.
- Look for a carbon monoxide shut-off feature and recent safety certifications.
- Decide on fuel: propane, gasoline or dual fuel.
- Check the runtime at half load, and plan how much fuel you will need.
- Consider noise, weight, wheels and electric start.
- Buy a heavy-duty outdoor-rated extension cord and a generator-safe place to run it.
- Plan fuel storage, and keep a log of when you ran the generator and rotated the gas.
Frequently Asked Questions
Is propane or gas better for a generator?
Propane stores for years and burns cleaner. Gasoline is easier to buy in normal times and usually gives slightly more power. A dual-fuel model gives you both.
How long does gasoline last in storage?
Untreated gasoline can start to degrade within a few months. A stabilizer extends the life, and many sources suggest rotating fuel at least every six to twelve months.
Can I run a generator in my garage?
No. Never run a generator in a garage, basement, shed or any enclosed space, even with the doors open. Use it outside at least 20 feet from the house.
How much propane is in a 20-pound cylinder?
About 4.7 gallons when filled to roughly 80 percent.
Do I need a transfer switch?
If you want to power your home wiring, yes, and it must be installed by a licensed electrician. Never plug a generator into a wall outlet.
Bottom line
Pick the generator that matches your outage plan: dual-fuel for flexibility, propane for storage and gas for output. Whichever you choose, run it outside, away from the house, with CO alarms inside, and test it regularly.
