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Dual-fuel portable generators: size the propane number, not the gasoline one
Dual fuel is a selector, not extra watts. Westinghouse's WGen9500DF is 9,500 running watts on gasoline and 8,500 on propane. HomeGuide puts the portable at $500 to $2,500, or $900 to $4,000 once an electrician hooks it to the house. Ready.gov wants it 20 feet from the openings.
Dual fuel means one engine and a switch. Gasoline is one tank. Propane is the other. You do not get both wattages at once.
The box in the store is almost always the gasoline number. If your outage plan is a 20-pound cylinder because the gas stations are dark, that smaller propane rating is the machine you actually bought.
Fridge, sump, furnace is the load list. Whole-home vs essential-only is how much of the panel you intend to feed. This page is the fuel fork on a portable, not a pad-mounted standby.
Gasoline watts, then propane watts
Westinghouse publishes both numbers on the WGen9500DF, a common open-frame dual-fuel portable. On gasoline it is 12,500 peak watts and 9,500 running watts. On propane it is 11,200 peak and 8,500 running. That is 1,000 running watts gone when you flip the selector.
The same sheet says a 6.6-gallon gasoline tank runs up to 12 hours at 25 percent load, or 8 hours at 50 percent. A 20-pound propane tank is listed at about 7 hours at 50 percent load. Dry weight is 211 pounds. Total harmonic distortion is 23 percent or less, which is not inverter-clean power.
Westinghouse: WGen9500DF dual-fuel generator
Champion’s 2,500-watt dual-fuel inverter (model 201183) is the same pattern in a suitcase. The operator plate lists 1,850 running watts on gasoline and 1,665 on propane. That is roughly a 10 percent drop, same neighborhood as the big open frame.
Champion 201183 operator’s manual (PDF)
If the well pump, the freezer, and the furnace board add up to 9,200 running watts, the 9,500-watt gasoline sticker looks fine until you are on propane. Size the load against the fuel you will have on day two.
What the portable itself costs
HomeGuide’s 2026 generator guide puts a portable at $500 to $2,500 for the unit, or $900 to $4,000 once someone connects it to the house. Their size table puts a 2 to 5 kW portable at $250 to $1,400, and a 7 to 10 kW portable at $2,000 to $3,000.
By fuel, they list portable gasoline at $250 to $4,500 and portable liquid propane at $250 to $4,000. Those bands overlap on purpose. Dual fuel sits in both columns because it is still a portable engine.
Connecting to the house is a separate invoice. HomeGuide puts that hookup at $400 to $1,500, which is the transfer switch or interlock plus an inlet, not a pad and a gas trench. A transfer switch overall is $400 to $2,500. Heavy-duty 30- to 50-amp cords if you are plugging appliances in the yard are $30 to $200.
Transfer switch cost installed is the interlock vs ten-circuit vs 200-amp automatic fork. Never backfeed a dryer outlet.
Westinghouse lists the WGen9500DF at $1,249 MSRP on the product page. That is the manufacturer’s sticker, not a street price, and it is the machine only. Wheels, oil, and a propane hose are in the box on their spec. The 20-pound cylinder is not.
A propane tank for a standby is a different job. HomeGuide puts propane tanks at $400 to $1,800 on the generator page. That is a house tank, not the grill cylinder you already own. If you are rolling a portable, you are buying extra 20-pound bottles or a 40-pound, not a buried 500-gallon.
Fuel that sits vs fuel that gums
Gasoline is easy to buy until the neighborhood is dark. Then the stations have no power to pump. Ethanol blend also gums a carburetor if the tank sits for months.
Propane in a sealed cylinder does not go stale the way gasoline does. You can keep a couple of 20-pound bottles filled before hurricane week. The trade is output, hose fittings, and a tank that ices up if you try to pull too much vapor in January.
HomeGuide’s run-cost table is written for a generator sitting there all day, not for your exact engine. A 7 kW they put at $10 to $70 per day. Gasoline in that table is $55 to $70 for 7 kW. Liquid propane is $60 to $70 at 7 kW and $145 to $165 at 15 kW. Those are their fuel prices, not yours.
A portable is not a three-week machine on their chart. HomeGuide says portables should not run more than two consecutive days. Treat that as a service and cooling limit, not a law. If the ice storm is on day four, you are into oil checks, cool-downs, and a plan B.
Renting instead of buying is on the same page: $40 to $55 a day for 1 to 2.5 kW, $70 to $90 for 5 to 7 kW, $80 to $110 for 8 to 10 kW, fuel extra. A three-day ice storm on a 7 kW rental can land near the low end of buying a small dual-fuel unit, before you count that you still have no machine next year.
Twenty feet, not the garage
Ready.gov wants generators outdoors and at least 20 feet from windows, doors, and attached garages. Carbon monoxide detectors with battery backup go on every level. Let the engine cool before you refuel, because fuel on a hot muffler is a fire. Keep the unit dry. Use heavy-duty cords, not a lamp cord from the junk drawer.
Ready.gov: power outages and generator safety
CPSC says never run a portable inside a home, garage, basement, crawlspace, or shed, even with the door open. One portable generator makes as much carbon monoxide as hundreds of cars. They put more than 100 U.S. deaths a year on portable generators. If a CO alarm sounds, get everyone outside to fresh air and call 911. This page does not diagnose anything.
CPSC: generators and engine-driven tools
Look for a unit that shuts off when it sees high CO. CPSC points at PGMA G300-2018 and UL 2201. Those labels are about shutting the engine down, not about putting it in the garage.
Generator placement is the yard conversation, including the neighbor who lives with the exhaust. Dual fuel does not change the 20-foot rule. Propane exhaust is still carbon monoxide.
Open frame vs inverter
The WGen9500DF’s THD at 23 percent or less is typical of an open-frame home-backup portable. That is fine for a fridge compressor, a sump, and many furnace boards. It is a poor match for a desktop PC, a variable-speed well pump, or anything the manual calls “sensitive electronics.”
Portable power station vs inverter generator is the quiet suitcase fork. Dual-fuel inverters exist. Champion’s 201183 is one. You pay for cleaner power and less noise, and you give back a lot of running watts.
If you need 240 volts for a well, you need a 240-volt outlet on the generator (L14-30R or 14-50R) and a transfer path that is not a cord stuffed into a dryer outlet. The Westinghouse unit has both a 30-amp twist-lock and a 50-amp outlet. The suitcase inverter often does not.
Generator quiet spec vs the real yard is why a brochure decibel is not the lot-line number. Open-frame dual fuel is a small engine. Plan for it.
What usually blows the dual-fuel number
Sizing against gasoline, then running propane. The 9,500-watt sticker and an 8,500-watt propane rating are not a rounding error when the well and the freezer start together.
Buying the machine and skipping the switch. HomeGuide’s connected-to-house band is $900 to $4,000 because the inlet and the interlock are the other half. Extension cords through a cracked window also dump exhaust toward the opening Ready.gov told you to keep 20 feet from.
One 20-pound bottle and a three-day outage. Westinghouse’s own 50-percent propane figure is about 7 hours on that tank. You want extras, filled, before the storm, and a way to swap them without standing over a hot engine.
Gasoline left in the carb all summer. Dual fuel does not magically keep the gasoline side clean. If propane is the plan, run the carb dry after the last gasoline use, or you own a no-start in October.
THD nobody mentioned. A 23 percent open frame into a new variable-speed furnace can be an expensive lesson. Ask the furnace brand what they want, or put the board on a small inverter and leave the open frame for the well.
Weight. 211 pounds plus a full tank is not a “portable” you carry upstairs. It is a rolling cart and a ramp, or it lives on a pad under a cover and you still treat the exhaust like a car.
Permits. HomeGuide puts generator permits at $80 to $450. Some towns care about a cord in the yard. Some care the minute you land an inlet on the panel. Ask before you cut the siding.
What the driveway questions sound like
Which running-watt number is on propane, not just gasoline, and where is that on the spec sheet?
Does this unit have a 240-volt outlet if the well or the dryer circuit is on the list, and which plug is it?
Is there CO shutoff, and is it listed to PGMA G300 or UL 2201?
Where will it sit, measured to the nearest window, door, and garage opening, with the exhaust pointed away?
Who installs the inlet and the interlock or transfer switch, and is that bid in writing separate from the generator box?
How many 20-pound cylinders do you already own, and how many hours is the maker claiming at half load on one of them?
How do I decide this week?
Add the running watts on the fuel you will actually have. If propane is the plan, ignore the gasoline headline.
Price the machine and the hookup as two lines. HomeGuide’s portable is $500 to $2,500 on the cart and $900 to $4,000 once it can feed the house.
Keep the engine 20 feet out, exhaust away, CO alarms on every floor. That is Ready.gov, not a brand brochure.
Match the power quality to the load. Open-frame dual fuel for the well and the fridge. An inverter, or a power station, for the electronics the furnace maker is picky about.
Count cylinders before the storm, not during it. One 20-pound tank is an afternoon at half load on the Westinghouse sheet, not a weekend.
If the outage you fear is a week of ice and you want the house to start itself, that is a standby on natural gas vs propane vs diesel, not a cart you roll out in the rain.