Backup generator installation
Published October 3, 2026.
Built by Jeremy Panasuk.
Plugging a cord into an appliance is not an installation. Tying the generator to the building is, and that step is an electrician's.
What gets installed
A portable generator can feed a few appliances through the cords OSHA describes: the manufacturer's cords, or grounded extension cords rated for the load, inspected so they are not cut or frayed. That path stops at the plug.
Feeding circuits inside the house is the installation. OSHA says attaching a generator to a building's electrical system without a properly installed transfer switch can energize wiring for a long distance and creates an electrocution risk for utility workers and others. The amp-class math for 30 A versus 50 A is already on transfer switch sizing: the site's planner treats 30 A as 30 × 240 V = 7,200 W and 50 A as 50 × 240 V = 12,000 W. This page uses those same thresholds on one published appliance pair.
Worked example: electric dryer and one range element
Honda lists an electric clothes dryer at 6,750 starting watts and 5,400 running watts, and an 8-inch electric range element at 2,100 starting watts and 2,100 running watts. Both rows are marked 240 V.
Generator tab, both loads on, 20% headroom:
- Running total = 5,400 + 2,100 = 7,500 W.
- Largest start is the dryer at 6,750 W. Extra surge = 6,750 − 5,400 = 1,350 W.
- Peak = 7,500 + 1,350 = 8,850 W.
- 8,850 × 1.20 = 10,620 W, rounded up to the next 500 W = 11,000 W recommended.
- Gasoline at 50% of that recommendation = 11,000 / 7,000 = 1.57 gallons per hour. A 4 gallon tank lasts 2.5 hours. That short tank time is the portable formula applied to a large class. It is a reason this pair is a bad fit for a small gasoline portable, not a diesel burn rate.
Transfer-switch planner, which adds the watts you type and does not add surge. Enter the running watts the way the script parses a line (Name - watts):
- Dryer - 5400
- Range element - 2100
Total = 7,500 W. The first class in the planner that is at least 7,500 W is 50 A / 12,000 W. The 30 A / 7,200 W class is smaller than 7,500 W, so this list does not fit it. An 11,000 W generator recommendation also sits under the 12,000 W ceiling and over the 7,200 W ceiling.
A common mistake
Buying the generator, then plugging it into a dryer outlet to "backfeed" the panel. FEMA's line is not to plug the generator into a wall outlet or the main panel. OSHA's line is that the transfer switch has to be installed by a qualified electrician. The 11,000 W figure does not make a suicide cord safer. It makes the cord more dangerous.
Limits, and when to call a pro
This page does not design a service, pick a breaker, or say your jurisdiction's permit fee. It shows one pair of Honda rows through two tools you already have. A standby set with an automatic transfer switch, a concrete pad, and a fuel line is a larger job than this cord-versus-switch distinction. Use the commercial service checklist when the machine is a stationary unit, and the safety page for the 20-foot placement rule that still applies after the electrician leaves.
Compiled with AI assistance from the sources below. Spot an error? Email [email protected].