Generator Sizing and Safe Use After a Hurricane

In several recent hurricane seasons, carbon monoxide poisoning from portable generators caused more deaths in the days after landfall than the storm's wind and water did during it. Almost every one of those deaths was preventable, and almost all of them involved a generator running in a garage, on a porch, in a breezeway, or under an open window.

The safety rules, first

Never run a generator indoors. Not in a garage with the door open, not in a carport, not in a shed, not on a covered patio. A portable generator can produce as much carbon monoxide as hundreds of idling cars. CO is colorless and odorless, and it accumulates.

Twenty feet minimum, exhaust pointed away. Place the generator at least 20 feet from the house with the exhaust directed away from doors, windows, and vents — including your neighbor's. CO from an adjacent property has killed people in their own homes.

Install battery-powered CO alarms. One on each level of the house and outside sleeping areas. Test them at the start of hurricane season. This is a twenty-dollar purchase that is the difference between a headache and a fatality.

Never backfeed. Plugging a generator into a wall outlet to energize the house sends power backward into the utility lines and can electrocute line workers restoring your neighborhood. It is also illegal in most jurisdictions. If you want to power circuits rather than individual appliances, have an electrician install a transfer switch or an interlock kit.

Let it cool before refueling. Gasoline spilled on a hot engine ignites. Shut the generator down and give it several minutes before adding fuel.

Keep it dry. Operate on a dry surface under an open canopy structure — not a tarp draped over the unit, which traps heat and exhaust. Never touch a generator with wet hands.

Sizing: how much generator do you need?

Generators are rated in running watts (continuous output) and starting watts (a brief surge for motor-driven appliances). You size to the sum of running watts for everything you will run at once, plus the single largest starting surge.

Typical figures:

• Refrigerator or freezer: 150-200 running watts, 800-1,200 starting
• Window air conditioner (10,000 BTU): 1,200 running, 1,800 starting
• Central AC (3 ton): 3,500 running, 6,000+ starting
• Well pump (1/2 hp): 1,000 running, 2,100 starting
• Sump pump: 800 running, 1,500 starting
• Box fan: 100 running
• LED lights, phone and laptop charging, router: 200-400 combined
• Microwave: 1,000-1,500
• CPAP machine: 60-200

Three practical tiers:

2,000-2,500 watts (inverter). Runs the refrigerator, fans, lights, communications, and medical devices like a CPAP. Quiet, fuel-efficient, and light enough to carry. This covers the actual necessities for most households.

5,000-7,500 watts. Adds a well pump, sump pump, a window AC unit, and a microwave. This is the common sweet spot for a house on a well or in a flood-prone area.

10,000+ watts or a standby unit. Required for central air conditioning. Standby generators run on natural gas or propane, start automatically, and are permanently wired through a transfer switch. They cost several thousand dollars installed but eliminate the fuel-hauling problem entirely.

Fuel

A 5,000-watt generator at half load burns roughly 0.5 gallons per hour, or about 12 gallons a day if run continuously. Running around the clock is usually unnecessary — cycling it for a few hours at a time keeps a well-packed refrigerator cold and stretches fuel dramatically.

Store gasoline in approved containers, outside living space, treated with a fuel stabilizer. Untreated gasoline begins degrading in about 30 days; stabilized fuel lasts a year or more. Rotate it into your car at the end of each season. Remember that gas stations need electricity to pump; the window to buy fuel closes before landfall, not after.

Propane stores indefinitely and does not gum carburetors, which makes dual-fuel generators attractive for equipment that sits unused for eleven months a year.

Maintenance that actually matters

The most common generator failure is not mechanical — it is a machine that was bought, used once, and stored with fuel in the carburetor, where it varnished. Every three months: start the unit and run it under load for 20 minutes. Before the season: change the oil, replace the air filter, check the spark plug, and confirm you have a spare oil supply and extension cords rated for the load.

Use heavy-gauge outdoor-rated extension cords, 12-gauge or thicker for long runs. Thin cords overheat and drop voltage, which damages appliance motors.

The alternative for small loads

For phones, radios, lights, and a CPAP, a large lithium power station plus a couple of solar panels does the job silently, indoors, with zero CO risk. It will not run a refrigerator for long, but paired with a small generator that charges it during a short daily run, it is an efficient combination.

Power is one item on a much longer list. See where your household stands with the free preparedness checklist.