Inverter or conventional generator: which one do you need?
Both types burn fuel to spin an alternator. The difference is what happens to the electricity before it reaches your outlet, and that decides what you can safely plug in.
How a conventional generator works
A conventional (open-frame) generator runs its engine at a fixed speed, usually 3,600 rpm, to hold the output at 60 Hz. The power is usable for tools, pumps, lights and appliances, but its waveform is less clean, and the engine runs at full speed even when you only draw a few hundred watts. That makes it loud and thirsty at light load, but it gives you the most watts for the money.
How an inverter generator works
An inverter generator converts its raw output to DC, then electronically rebuilds a clean AC sine wave. Manufacturers typically quote total harmonic distortion under 3%, which is what sensitive electronics expect. Because the frequency is set by the electronics, the engine can slow down when demand is low. The result is lower fuel use, much lower noise and a smaller, lighter machine for the same continuous output.
Which one should you buy?
- Choose an inverter for camping, RVs, tailgating, and home backup of computers, TVs, routers, medical devices and modern furnaces with electronic controls.
- Choose a conventional generator for job sites, well pumps, power tools and whole-home backup where you need 8,000 watts or more on a budget.
- Consider both in large inverter models: units of 7,000–11,000 watts now combine clean power with enough output for most homes, at a higher price.
Sizing: running watts and starting watts
Add the running watts of everything you need at the same time, then add the single largest starting surge. Motors (refrigerators, well pumps, air conditioners) can briefly draw two to three times their running watts when they start. A generator that covers the running total but not the surge will stall or trip every time the compressor kicks in.
Fuel choice
Dual-fuel and tri-fuel models run on gasoline and propane, and some also on natural gas. Propane stores for years without going stale and avoids carburetor problems in a generator that sits unused between storms. Gasoline gives slightly more power per tank. Whatever the fuel, a generator must always run outdoors, far from doors, windows and vents, because of carbon monoxide.
Connecting to your house
To power house circuits, you need a transfer switch or a panel interlock installed by a licensed electrician. Never back-feed a panel through an outlet: it can electrocute utility workers and damage the generator.