Inverter generator vs regular generator: what's the difference?

Both kinds burn gas or propane and spin an alternator. The difference is what happens to the power next, and what the engine does when you unplug things.

The short version

	Inverter generator	Conventional (regular) generator
Power quality	Clean: makers list 3% THD or less	Rougher: makers list about 12% to 23% THD
Engine speed	Speeds up and slows down with the load	Runs at a steady speed
Noise	Quieter, often in a closed case	Louder, usually an open frame
Fuel at light loads	Uses less	Uses more
Weight	Lighter for its size	Heavier
Big sizes and 240 V	Fewer options, some 120 V only	Common, often with L14-30 and 14-50 outlets

How an inverter generator works

Champion explains it simply. A conventional generator sends its "raw power" straight to the outlets. An inverter generator converts the power to direct current (DC), then back to alternating current (AC). That extra step lets it make clean, steady power, with total harmonic distortion (THD) of 3% or less.

A small computer also adjusts the engine speed to match the load. Plug in one lamp and the engine idles down. Start the microwave and it speeds up. That's what "eco mode" does on many models.

What's THD, and does it matter?

THD measures how far the power's wave shape is from a smooth, pure sine wave. Lower is cleaner. Even utility power has some.

Champion's FAQ says standard generators put out about 12% to 20% THD, depending on load. One maker's 7,500 W open-frame generator lists 23% or less. That FAQ says this is fine for most household things, like TVs, computers and appliances.

It also lists things that may need under 3% THD:

• a UPS-style battery backup
• a pellet stove
• a high-efficiency furnace control board

If any of those matter in your house, an inverter generator is the safer bet. Check your furnace or stove manual too.

Noise: how much quieter?

Here's what two makers publish:

Generator	Maker's noise figure
Small inverter, 1,800 running W	52 dBA (distance not stated)
Small inverter, 1,700 running W	53 dBA from 23 feet
Open frame, 7,500 running W	72 dBA (distance not stated)

A 20 dB gap is big. But only compare figures taken at the same distance and load, which makers don't always state.

Fuel: inverters win at light loads

Because their engines slow down, inverters stretch fuel when you're only running a few things.

Generator	Maker's run time	Hours per gallon
Small inverter, 1,800 running W	12 h at 25% load on 1.14 gal	about 10.5
Open frame, 7,500 running W	11 h at 25% load on 6.6 gal	about 1.7

These aren't the same size, so it's not a fair head-to-head. But it shows the idea. A small inverter running a fridge and some lights sips fuel. A big open-frame generator running the same small load burns much more, just to keep its engine at full speed. See how long a generator runs on 5 gallons.

Power and 240 V: conventional usually wins

For whole-house-style backup, you often want lots of watts and a 240 V outlet.

• The 7,500 W open-frame model above has an L14-30 twist-lock outlet for a transfer switch or interlock.
• Many small inverters have only 120 V outlets.
• Larger inverters exist too. One maker lists an 8,500 W dual-fuel inverter, for example.

If you need 240 V for a well pump or to feed your panel, check for an L14-30 or 14-50 outlet before you buy. Our 30 vs 50 amp cord guide explains them.

Weight and moving it

The 1,800 W inverter above lists 47.4 lb. The 7,500 W open-frame lists 197.1 lb, with wheels. A small inverter is easy to carry to a campsite. A big open-frame is something you roll out of the shed.

Which one should you pick?

Choose an inverter generator if:

• you want quiet for camping, an RV, or close neighbors
• you'll run light loads: a fridge, lights, phones, a CPAP
• you have electronics or a furnace board that want clean power
• you want to carry it

Choose a conventional generator if:

• you need a lot of watts for the money
• you need 240 V for a well pump, or to connect to a transfer switch
• noise and weight don't matter much

Not sure how many watts you need? Use the calculator above. It's pre-filled with a fridge, furnace fan, TV, router, chargers and lights. Then see our size guide.

What about a power station instead?

If you mostly need quiet, light loads for a night or two, a battery power station might suit you better. It has no engine at all. Compare them in portable power station vs generator.

Both inverter and conventional generators make deadly carbon monoxide. Run either one outdoors only, at least 20 feet from your home. Read our generator carbon monoxide safety guide.