Portable Generators for Winter Outages: Size, Fuel and Placement

Size a portable generator by adding the running watts of everything you plan to power, then adding the single highest starting wattage, the method Champion Power Equipment publishes. Choose a model with a CO shut-off feature, as CPSC recommends, and run it outdoors only, at least 20 feet from the house.

How do you figure out what size generator you need?

Champion Power Equipment, a generator maker, lays out the sizing method in five steps:

1. List every appliance and device you plan to run at the same time.
2. Find each one’s running watts on its label, or calculate them if only volts and amps are listed.
3. Add all the running watts together. That is your base load.
4. Find the highest starting wattage among those appliances.
5. Add that starting figure to your running total. That is your peak need.

Champion defines running watts as the continuous power a device needs once it is on. Starting watts are the extra burst some devices need to start, which it says are typically 1 to 2 times the running wattage and last a fraction of a second.

The American Red Cross gives the same core advice: add up the power needs of what you want to run, checking the label on the back or sides of each appliance. It notes that some machines draw up to 3 times as much power when starting. Champion suggests choosing a generator that beats your calculated total by a safe margin for unexpected surges.

How many watts do common winter appliances use?

Champion publishes typical ranges for household appliances. Your appliance’s own label is the better number, but these ranges show which loads matter.

Champion’s note on the rows marked “None listed” is that those appliances do not need extra starting watts, so you size them on running watts alone.

A worked example for a winter outage

Take the upper end of each range for a cautious estimate. Say you want a refrigerator, a 1/2 HP furnace fan, six LED bulbs, a router and a laptop charger.

• Running watts: 400 + 800 + 90 + 20 + 100 = 1,410 W
• Highest starting wattage: the furnace fan, at 1,600 W
• Peak need: 1,410 + 1,600 = 3,010 W

Add a 1,500 W space heater and the running total climbs to 2,910 W, with a peak of 4,510 W. Heaters are some of the biggest loads on the list. If you plan to run one, read how to use a space heater in a power outage first, since heater safety rules limit how you can connect it.

The Red Cross also suggests staggering when you run appliances to avoid overloading the generator.

Inverter or conventional generator?

Champion describes inverter generators as quieter and lighter than standard portable generators, producing clean, stable power suited to sensitive electronics such as phones and laptops. Whichever you pick, confirm its running watts cover your peak number from the steps above.

Dual fuel models run on either gasoline or propane. Check the manual for the rated output on each fuel.

What does a CO shut-off feature do?

CPSC recommends portable generators with a carbon monoxide shut-off safety feature. In a May 2026 release, it said these features automatically shut off the generator when dangerous CO levels build nearby.

The same release said models certified to the latest PGMA G300-2023 and UL 2201-2023 standards include CO safety technologies designed to significantly reduce the risk of CO poisoning. CPSC added that UL 2201 certified models also have reduced CO emissions. Its consumer flyer says to ask the retailer for a model with automatic CO shut-off.

A shut-off is a backup, not a license to run the generator closer to the house. The placement rules below still apply.

Where do you put a portable generator in a winter storm?

CPSC says to operate portable generators outside only, at least 20 feet away from the house, and to direct the exhaust away from the home and other buildings. Its safety alert says to keep it at least 20 feet from doors, windows and vents that could let CO indoors. Ready.gov adds attached garages to the list of things to stay 20 feet from.

CPSC says never to operate a portable generator inside a home, garage, basement, crawlspace, shed or on a porch. Its safety alert explains why: CO can build to deadly levels in those spaces even with fans running or doors and windows open, and it can linger for hours after the generator shuts off.

Our carbon monoxide safety guide covers CO symptoms and exactly where CPSC and NFPA say to put alarms.

What about snow, rain and wet ground?

CPSC warns that generators pose a risk of shock and electrocution, especially in wet conditions. Its safety alert says to protect the generator from moisture without running it indoors or near openings to any occupied building. It suggests an open, canopy-like structure on a dry surface where water cannot reach it or puddle or drain under it.

CPSC also says to dry your hands before touching the generator. Ready.gov says to keep it dry and protected from rain or flooding, and to follow the manufacturer’s instructions carefully.

How do you store and refuel generator fuel safely?

CPSC’s safety alert says never to store generator fuel in the home. Gasoline, propane and other flammable fuels belong outside living areas in properly labeled, non-glass safety containers. Do not store them near a fuel-burning appliance, such as a natural gas water heater in a garage.

The American Red Cross says to use the fuel type named in the instructions or on the generator’s label, and to store it in an approved safety can. It also notes that local laws may restrict how much fuel you can store, or where. Your local fire department can tell you the rules.

Before refueling, CPSC says to turn the generator off and let it cool down. Gasoline spilled on hot engine parts could ignite.

How do you connect a generator to appliances?

Plug appliances straight into the generator, or use cords that meet CPSC’s rules:

• Heavy-duty extension cords designed for outdoor use.
• A wattage rating on each cord that exceeds the total wattage of everything plugged into it.
• Long enough to keep the generator outdoors and far from windows, doors and vents.
• No cuts or tears along the whole length, and a plug with all three prongs.
• Protected from pinching or crushing where it passes through a window or doorway.

CPSC says never to power house wiring by plugging a generator into a wall outlet, a practice called backfeeding. It calls this extremely dangerous and an electrocution risk to utility workers and neighbors on the same transformer. The American Red Cross says that if you want to connect a generator to house wiring, have an electrician install a power transfer switch that meets the National Electrical Code and local codes.

Is a battery power station a better fit?

For small loads such as phones, a router, LED lights and a CPAP, a battery power station is another option. Our sister site Solar Home works through the math in what size solar generator you need. Compare that with the table above: a space heater or well pump uses many times more power than a router or a phone charger.

What else should you have before the storm?

• CO alarms. CPSC says to install battery-operated CO alarms or alarms with battery backup outside sleeping areas and on each floor, and to test them monthly.
• A maintenance check. CPSC says to make sure the generator has been properly maintained and to read the labels, instructions and warnings before an outage.
• A plan for pipes. If the heat fails anyway, our guide on how to prevent frozen pipes lists the Red Cross steps.

For the rest of your outage and storm checklist, see our winter storm preparedness guide.