Dual Fuel Generators for Home Backup

Why dual fuel makes sense for outages

The problem with a gas-only generator isn't the generator. It's the fuel. Gasoline begins to break down in roughly a month, so Generac says to add stabilizer from day one. Even stabilized, Westinghouse puts the safe limit at about six months in the tank, and only with the carburetor float bowl drained. Most people's generator sits for a year between storms with old gas in it, and that's the generator that won't start.

Propane doesn't go bad. You can keep a few full cylinders by the shed, swap them as the outage goes on, and keep gasoline as the second fuel when the cylinders run out. During a long outage, when gas stations have no power to pump, having two fuels is real insurance.

What you give up on propane

Propane carries less energy per unit than gasoline, so output drops. Champion's published numbers for its 4000-watt dual fuel inverter show the pattern:

Expect a similar gap on other models and check the spec sheet for both columns. Size your loads to the propane column, and you'll have headroom when you switch to gas.

Watch how run times are quoted. Westinghouse measures propane run time at 50% load for its traditional generators and at 25% for inverters. Two run-time claims may not mean the same thing, so compare them at the same load.

Dual fuel options compared

For a house on a well, an open-frame dual fuel unit with enough propane running watts to start your pump is the practical pick. Check the pump's surge: Champion lists a 1/2 HP well pump at 1,500 to 2,000 starting watts. Run those numbers on our generator sizing page.

Features worth paying for

Electric start. Pull-starting a cold engine in a storm is the step most people dread, and a dead battery is the usual failure. Champion's 4000-watt model has push-button start with the battery included and a recoil backup. Keep the battery on a maintainer between outages.

CO shutoff. CPSC recommends generators that shut off automatically when CO builds up. Champion calls its version CO Shield and states it doesn't replace an indoor CO alarm.

The right outlet. If you plan to connect to the house, you need the outlet that matches an inlet box. Champion's inlets come in 30-amp and 50-amp versions for the L14-30 and 14-50 outlets. Many small inverters only have household and RV outlets. The 4000-watt Champion, for example, has a 5-20R duplex and a TT-30R RV outlet.

A fuel selector you understand. Read the manual for how your unit changes fuels, and practice the switch on a sunny afternoon, not in the dark.

What to skip

• Converting a gas-only generator to propane. Champion says a gasoline-only generator won't run on propane, and modifying it voids the emissions warranty.
• Tiny cylinders. Champion recommends 20 to 40 lb tanks for dual and tri fuel units. Small camping canisters won't get you through a night.
• Chasing the gasoline wattage. It's the bigger number, and it's the one on the box. Your long-outage number is the propane one.

Cost

HomeAdvisor's cost data puts propane portables at $600 to $2,600 and gasoline units at $500 to $3,000. Add the cylinders, a regulator hose if it isn't included, and the electrician's work if you're connecting to the panel.

Hooking it up

On the electrical side a dual fuel generator connects like any portable: cords to appliances, or an inlet box plus an interlock kit or transfer switch on the panel. Fuel choice doesn't change any of that.

Keep cylinders upright and outdoors, away from the exhaust. Keep spare gasoline out of the house in labeled safety cans, and shut the engine off and let it cool before you refuel or swap fuels.