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Inverter or open frame: which kind do you need?
Updated
An open-frame generator is an engine and an alternator in a steel cage. It gives you more watts than an inverter model, and the big ones have 240 volts. An inverter generator makes power, cleans it up with electronics, and sits in a closed shell. It is quieter, lighter and easier on electronics, but you get fewer watts.
Side by side
| Inverter | Open frame | |
|---|---|---|
| Noise | Lower. Engine slows down when the load is light | Higher. Engine runs at full speed all the time |
| Power quality | Both inverter picks here claim less than 3% THD | The open-frame listings we read gave no THD figure |
| 240 volts | Not on the inverter picks here | Yes on both open-frame picks here |
| Weight of our picks | 39 to 104.7 lb | 135.6 to 210 lb |
| Best use | Camping, RVs, essentials during an outage, close neighbors | Large home backup through a transfer switch |
What THD means
THD stands for total harmonic distortion. It is a measure of how smooth the power is. Lower is better. Laptops, furnace control boards and some newer appliances can act up on rough power. If you plan to plug electronics straight into the generator, an inverter is the safer bet. The Westinghouse iGen5000DF and Champion 4000-Watt both list less than 3% THD as a maker claim.
Read noise claims with care
- A dBA number means little without a distance and a load. Champion gives one: 64 dBA from 23 feet. Westinghouse says "as low as 52 dBA" for the iGen5000DF, and "as low as" points to a light load.
- WEN describes the 56235i as about as loud as a normal conversation. We saw no dBA figure in the part of the listing we read.
- Neither open-frame listing we read gave a noise figure. Owners of the WGen5300DFcv are split. Some call it quieter than most, some call it a little loud.
- Campgrounds often set quiet hours and noise limits. Check the rules where you camp.
Parallel kits
Some inverters can be linked in pairs for more power. The Champion is parallel ready, with the kit sold separately. The iGen5000DF is listed as parallel capable. Two small units can be easier to lift and store than one big one, and you can take just one camping. The catch is cost: you buy two generators and a kit. Only pair models the maker says are compatible.
CO shutoff sensors
Many newer generators shut themselves off when carbon monoxide builds up around them. On the listings we read, the Champion and the WGen5300DFcv name this feature. It is a backup, not a permission slip. It does not make it safe to run a generator in a garage or near a window. On another CO-sensor model we looked at, the review summary mentioned units shutting down for CO. If that happens, treat it as a warning that exhaust is collecting around the generator, and move it to more open air.
Safety first, every time
- Carbon monoxide kills. Never run a generator indoors, in a garage, in a shed or on a porch, even with the door open. Keep it at least 20 feet from the house. Point the exhaust away from windows, doors and vents. Put battery CO alarms inside your home.
- Never backfeed. Do not plug a generator into a wall outlet or dryer outlet. It can kill a utility worker or a neighbor and can start a fire. To power home circuits you need a transfer switch or an interlock kit, installed by a licensed electrician.
- Without that, run heavy-duty outdoor extension cords from the generator straight to each appliance.
- Let the engine cool before you refuel. Store fuel outside the house.