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4 and a Half stars

Review of the WEN GN400i RV-Ready Open Frame Portable Inverter Generator

4750 Starting Watts, 3750 Running Watts on Gasoline

Electric Start: No

Weight: 66.1lbs

Noise: 67dB


Should You Buy It?

This is a popular generator with a fair amount of power. It's well-built and great value for money when compared to one of the more premium brands. 

If you need clean power the GN400i can deliver, this is a good candidate for a reasonable amount of money. And don't forget, those power outputs can be increased owing to its parallel capability.

Because there is neither a wheel kit option nor electric start, this model will not suit everyone.

Key Points about the WEN GN400i

Compact and lightweight design
Parallel capable
Value for money
Easy setup and operation
Safe for use with sensitive electronics
Open frame so noisier
No hour meter or electric start
No wheel kit
Oil change every 25 hours
Uneven Customer Service

Overview of the Generator


In the GN400i WEN offer you an open frame generator with a compact, lightweight, and innovative design. Its inverter technology delivers clean power, and it's ideal for light work on a jobsite, campsite, with your RV, and as a basic emergency backup. In the home, when the need arises, it can run a fridge, heaters, lights, freezer, and computers.

Controls and Features


The control panel is fairly minimal but very practical. Among its features are an engine switch, LEDs for low oil, overload and readiness, an ECO-Mode and for a parallel connection. The ECO-Mode adjusts the engine speed automatically to match the load demand, increasing fuel economy and reducing noise/emissions.

You don't have an electric start option for this model, just a manual recoil cord.

The generator has an oil sensor which stops the engine when it's too low, and also prevents you from trying to start it until you've topped it up.

WEN say a feature of open frame generators is the accessibility of the fuel shut-off valve, important for using up the remaining fuel in the carburetor.

For equipment connection, it includes 2x120v NEMA 5-20R receptacles, 2x5v USB ports, and 1x120v RV-ready TT-30R receptacle.

With EPAIII Certification and CARB Compliance the GEN400i can be used in all 50 states. It's also safe for use in National Parks and camp sites as the muffler incorporates a spark arrestor as standard.

It can run for up to 7 hours at 50% load on its 1.85-gallon fuel tank.

WEN offer a 2-year warranty on all their inverter generators.

For more detailed information on this model, have a look at the WEN GN400i manual.

Power Output

The generator is powered by a 212cc OHV engine producing 4000 starting watts and 3500 running watts. These outputs can be increased by connecting another GN400i in parallel using the optional Parallel Kit.

The power output on this model, with inverter technology, is clean. This means it's a good option if you power a lot of sensitive electronics.

Several high-altitude kits are available if you intend to use the generator between 2000 and 8000 feet. And take note, altitude can have a significant impact on the power outputs of any generator.


Weighing 66.1lbs, this is a relatively light open frame generator. But it's not light enough for one person to carry comfortably. Unfortunately, it has no wheel kit supplied, and this isn't an option you can buy separately as an add-on. In the absence of wheels, at least one owner has built a cart on which to move the generator from place to place.

Noise Level

WEN don't mention the noise level in the manual for this model. Built with an open frame, it's bound to be noisier than an inverter built with a closed frame. One owner, however, says it's about 60-62 dB at 20 feet, and under 70dB standing next to it. Elsewhere a figure of 67dB is mentioned.

What Most Buyers Like

The GN400i is a well-built inverter generator that represents excellent value for money. The instruction manual is clear and well-written, which is not always the case with other manufacturers.

Being an open frame it's much easier to work on compared to the hassle of opening closed frame models.

Although it doesn't come with engine oil, the box has all the tools to prepare the machine, including a funnel and hose to fill the oil without making a mess.

What Some Buyers Like Less

Fuel economy is disappointing, with only a 3-hour gain at 25% load over the quoted 7 hours at 50% load. A larger fuel tank would allow the generator to run for more than 7 hours.  And there is some disappointment in the recommendation for owners to change the oil every 25 hours. In fact, the manual recommends oil changes more often in dusty conditions or operating under heavy loads. 

According to one owner, who returned the generator, WEN don’t answer emails and their Customer Service kept him on hold for almost an hour. Others also say they had unsatisfactory service when faced with problems.

Several owners say the generator is very loud, "like a MACK truck", even before adding any load. They worry about annoying neighbors. One says he's building a noise box to keep the racket down. Others, however, say the noise isn't too bad, underlining what we say about our individual perceptions of noise.

Starting Watts4000
Running Watts3500
Noise Level67dB
Rated Voltage120V AC
Rated Amperage26.6A
Engine Type4-stroke, OHV, single cylinder
Cooling SystemForced air
Gas Tank Capacity1.85 US Gallons (7 L)
Oil Capacity17 fl. oz. (0.5 L)
Run Time 50% Gas7 Hours
Spark Plug TypeTorch F6RTC/NGK BPR6ES
Spark Plug Gap0.7 - 0.8 mm (0.028 - 0.031 in)
Spark Plug Torque1/2 - 3/4 turn after gasket
contacts base or 15 ft-lbs
Carb CompliantYes
EPA III CertifiedYes
Dimensions (inches)19.8 x 13.8 x 18.9 (L x W x H)