Running a portable generator safely during an outage

Why this matters

A portable generator is a small gasoline engine bolted to an alternator. It makes useful power, and it also makes carbon monoxide, heat and a fire hazard. Most generator injuries happen in the first hours of an outage when people are rushed, cold and working in the dark.

This guide covers the safe operating side. It assumes your generator connects through an inlet and transfer switch or interlock. If it does not, read why backfeeding is dangerous first.

Placement

Choose your generator spot in summer, not during a storm. It should be outdoors, on firm level ground, far enough from the house that exhaust does not drift in, and with the exhaust pointed away from the building.

• Stay well clear of windows, doors, soffit vents, furnace and water heater intakes and air conditioners. The manufacturer's manual gives minimum distances; follow the larger of that or whatever keeps exhaust out of the house.
• Watch wind direction. A west wind can push exhaust right back toward the house.
• Keep it out of standing water and drifting snow, but do not box it in. Use only a cover or tent the manufacturer approves.
• Install battery-powered or battery-backup CO alarms on every level and near sleeping areas, and test them before winter.

Cold-weather starts

At -25 C, a generator that sat untouched since spring may not start at all. A little preparation helps:

• Run it for a while every month or two so you know it works.
• Use the oil grade the manual recommends for cold temperatures, often a synthetic.
• Treat the fuel with stabilizer, or run the carburetor dry for storage if the manual recommends it.
• Keep the battery (on electric-start models) charged with a maintainer.
• Store it somewhere dry. Bring it out and start it before you need to connect it.

Cords and connections

Use one cord, the right one. It should match your generator's twist-lock receptacle and your inlet, be rated for the generator's output, and be long enough to keep the generator well away from the house.

• No household extension cords daisy-chained together.
• No splices, cuts or crushed jackets. Inspect the cord before every use.
• Keep the cord out of puddles and melt water, and do not pinch it in a door or window.
• If you run a few appliances directly from the generator instead, use outdoor-rated, heavy-gauge cords sized for the load.

Fuel and refuelling

• Shut the generator off and let it cool before refuelling. Spilled gasoline on a hot muffler can ignite.
• Store fuel in approved containers, outside the house, away from the generator and any flame.
• Store only what you can safely keep and rotate. Old gasoline causes hard starts.
• Keep a fire extinguisher suitable for fuel fires nearby.

If you find yourself refuelling a portable unit for days at a time every winter, it may be time to look at standby vs portable generators.

Before the next outage

Most of the work of running a generator safely happens on an ordinary day, long before the lights go out. A short checklist, done once each fall, makes the night of the outage calmer.

• Start the generator and run it under some load for a few minutes.
• Check the cord for cuts, crushed spots and damaged plugs.
• Confirm you have fresh, stabilized fuel and a funnel, stored safely outside the house.
• Test every CO alarm and smoke alarm in the house.
• Keep a headlamp, gloves and the changeover card where you can find them in the dark.
• Clear a path to the generator spot that you can shovel quickly after a storm.

If anything on that list fails, you have time to fix it before you need it. A licensed electrician can also check your inlet, interlock or transfer switch during a routine visit.

Load management by hand

A portable generator has limited capacity. Bring loads on one at a time, starting with the largest motor, usually the furnace blower or sump pump. Avoid starting several big motors at once.

Skip heavy heating loads like space heaters, kettles and toasters when the furnace is running. If lights dim sharply or the generator labours when something starts, turn something off. Your electrician can label which transfer switch circuits matter most so the choice is easy at night.

For help choosing the right size in the first place, see sizing a backup generator.

Common questions