Cummins Onan portable generators

The models with an i in the name are inverter generators. They rectify the engine output and rebuild a clean sine wave, which means low harmonic distortion and no risk to laptops, routers, modern televisions or anything with a variable-speed motor. They also throttle down under light load, so they are far quieter and burn noticeably less fuel when they are not working hard.

Conventional sets trade that for raw output per dollar. If the load is pumps, heaters and power tools, a conventional unit is the better buy. If the load includes anything with a circuit board, buy the inverter.

Dual fuel is worth the difference

Gasoline degrades within months and is the single most common reason a stored generator will not start when it is finally needed. Propane does not degrade at all. A dual-fuel unit kept on LP, with the gasoline system run dry, is dramatically more likely to fire on the first pull after sitting through a quiet year.

Do not back-feed without a transfer switch

Plugging a portable into a wall outlet to power house circuits back-feeds the utility line and can kill a lineman working to restore service. It is illegal and it is not a gray area. If you want a portable to run house circuits, we install a manual transfer switch or an interlock kit — and if you are already doing that work, it is worth asking whether a standby unit is the better purchase.