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Generac GP3500iO - Spec Review

The Generac GP3500iO (7128) is a compact and lightweight open frame inverter generator with a rated wattage of 3000 W and a starting wattage of 3500 W.

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Generac GP3500iOGenerac GP3500iOGenerac GP3500iO

Description

Portable generators are a welcome addition to many activities at home, at work, and away. In an emergency, portable generators can provide critical backup power. They make camping and tailgating more comfortable. And contractors appreciate the flexibility portable power brings to the jobsite. (source: Generac (opens in a new tab))

Zoom on the Generac GP3500iO

In summary, the Generac GP3500iO is a compact and lightweight portable inverter generator especially useful for:

  • RV travellers wishing to enhance their freedom and nomad lifestyle
  • People occasionally participating in outdoor fairs, festivals or events
  • Amateur DIY lovers
  • Homeowners who want to be able to use the most necessary devices in their household, even during a blackout
  • Camping and tailgating buffs looking to enhance their experience

In the sections ahead, the power characteristics, availability of various outlets, the portability, and any additional features of the device shall be discussed, including its emission compliance information.

Power & Run Time

The Generac GP3500iO in use

The Generac GP3500iO

The Generac GP3500iO's core is the 212 cc Generac OHV 4-stroke engine, which runs on gasoline. With an output of 120V, it provides a running wattage of 3000W and a peak wattage of 3500W. In addition, as it is parallel capable (GP3500iO Parallel Kit not included), this power can be doubled when linked to another similar or compatible unit.

The inverter generator features a simple traditional pull-start mechanism. It features Generac's PowerDial™, an easy-to-use dial with three operation settings.

Thanks to a fuel capacity of 2.37 gallons, the GP3500iO can operate for up to 11 hours with a full tank (fuel consumption around 0.22 GPH).

Delicate electronics can be plugged in an AC outlets safely, as the GP3500iO generates a clean sine wave, reaching a <3% Total Harmonic Disruption (THD).

Outlets

The control panel provides the upcoming 3 AC outlets:

Duplex 120V 20A (5-20R)
120V 30A (L5-30R) receptacle

In addition, it provides 2 DC outlets: there's two 5V USB ports with which you may charge electronics, for example mobile phones or tablets, conveniently.

Even though this Generac generator isn't quite RV Ready, its L5-30R receptacle allows an easy RV connection via an L5-30P to TT-30R adaptor.

Portability

The Generac GP3500iO has a conventional, open frame design, of the following dimensions: L19.3 x W16.9 x H16.4 in, which offers support and allows it to be raised above ground level. The generator is designed for ideal use outdoors and in rough environments.

The GP3500iO's dry weight of 74.3 lbs lets you use its power anywhere needed. Additionally, the generator’s mobility is also improved by its open frame design, as it can be easily grabbed and shifted.

Features

Panel of the Generac GP3500iO

The GP3500iO's control panel

To help you monitor the GP3500iO's status and activity, its control panel is equipped with a digital data center, giving you information on the lifetime run hours.

In addition to this info, several light indicators serve to show you when the generator is ready, the generator is on overload and its oil levels are insufficient.

As for its security measures, the device features an overload protection (circuit breaker) and an automatic low oil shut-off, letting you use it with a peace of mind.

Besides the classic documentation and an owner's manual (opens in a new tab) to get you promptly started, the Generac GP3500iO also comes with some accessories: tool kit, funnel and oil are included.

Emissions

The Generac GP3500iO is CARB-compliant. It can therefore be sold and purchased in all 50 states, including California.

Moreover, it features a spark arrestor and therefore, can be used in forested areas.

Product Videos

The Generac GP3500iO versus other generators

The following charts are provided to give you an idea of how some of the key specs of the Generac GP3500iO compare to generators of similar power (between 2500 and 3500 W).

  • As far as its dry weight is concerned, the Generac GP3500iO weighs just 74.3 pounds and thus, it is one of the lighter 2500 to 3500 rated wattage generators. In terms of weight, one of the champions in their power range is the Generac GP3300i, standing at just 59.5 lbs.
  • As for its autonomy, the GP3500iO, with an autonomy of up to 11 hours at a 25% load, is placed on the low end among the generators of its kind. If you consider autonomy on a single full tank as one of the deciding factors, one of the generators in the same power range that offers the highest run time is the Champion 200914, with up to 22 hours.
  • While the run time is an important parameter, it is dependent on the fuel tank’s capacity and thus, doesn’t say much on its own unless we consider fuel consumption as well. In fact, this inverter generator is not among the most fuel efficient, within the aforementioned wattage range : its estimated gasoline consumption at 25% load is around 0.22 GPH. If you wish to further improve in the area of fuel efficiency, the Energizer eZV3500P, which boasts with a gas consumption of only 0.13 GPH, may be the right generator for you.

Price comparison

As you can see from this interactive chart, when compared to other 2500-3500W generators, the Generac GP3500iO is on the average side of the price range.

Therefore, this generator nicely fits in the expected budget for this kind of product.

The bottom line

STRENGTHS:
  • In the expected price range
  • Several accessories included
  • Parallel capable
  • Inverter
  • Lightweight (74.3 lbs)
WEAKNESSES:
  • No electric start
  • Relatively low run time
  • Low fuel efficiency

Do you own the Generac GP3500iO and agree (or disagree) with these strengths and weaknesses?

Let us know and write your own review.

Features and Specifications

General
InverterYes
PortableYes
Parallel capableYes, cable not included
RV readyNo
FuelGasoline
Engine212 cc Generac OHV 4-stroke
Starting systemRecoil
Power
VoltageAC: 120V 60 Hz, DC: 5V
Running watts3000 W
Starting watts3500 W
Running amps25 amps
Peak amps29.2 amps
Run time @50% load8 h
Run time @25% load11 h
Features
GFCI outletsNo
Covered outletsNo
Automatic Voltage RegulationInverter
AC outlets
  • 1x Duplex 120V 20A (5-20R)
  • 1x 120V 30A (L5-30R)
DC outlets2x 5V USB port
Data centerLifetime run hours
IndicatorsLow oil, overload and output ready
Fuel tank2.37 gal
Fuel gaugeNo
Misc
Weight74.3 lbs
Approx. dimensions (L x W x H)19.3 x 16.9 x 16.4 in
Noise (lower limit)Unknown
THD< 3%
EmissionsCARB
SecurityLow oil and overload protection
Spark arrestorYes
NeutralFloating
Accessories includedOil, funnel, and tool kit
Warranty3 years
Other model numbers7128

Unlike many websites, we did our best to research each of the specs above. That being said, we are not immune to making the occasional mistake or omission. Should you notice any missing or incorrect values, don't hesitate to suggest improvements so we can address the issue.

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About Generac

Generac Power Systems is an American based generator and power equipment manufacturer, founded in 1959. As its name suggests, the main focus of Generac are power generators, and other related electric equipment, such as switches, paralleling systems and small engines. The company has several manufacturing facilities based in the US, thus, their products are made in the USA. However, the company provides no information about the origin of their components.

Warranty Information

The Generac GP3500iO is covered under a warranty for up to 3 years. This warranty may be limited and may not cover all parts of the generator.
For more information about the warranty of Generac generators, please consult Generac's warranty policies (opens in a new tab). Alternatively, you can also contact their Customer Support: 1-888-GENERAC (888-436-3722).

Questions & Answers

What can it power?
Examples of items that can be simultaneously powered.
The examples below are based on a maximum load of 80% and estimated wattages. For a more accurate estimation, use our generator sizer.
ItemRunning WattsStarting Watts
At homeRefrigerator (energy star)1921192
Hair dryer18001900
Blender400850
Total2392 W3392 W
For campingRadiant heater13001300
RV refrigerator180600
Toaster oven800800
Radio100100
Total2380 W2800 W
For workGrinder14002500
Reciprocating saw730960
Drain cleaner250250
Total2380 W3480 W
What is the noise rating of the GP3500iO?

Due to the lack of standardization in noise emission measurement, Generac does not provide their units' noise levels.

Does it have an eco mode? (Asked March 19th, 2020)

There is an economy switch that can be put to "ON" when running appliances or equipment that are resistive loads (non-motor starting), such as TVs, lights, laptops, etc.

I want a fuel shut off valve where do I find it (Asked September 24, 2020)

The "OFF" position of the PowerDial Switch stops the engine and shuts off fuel flow.

This unit is a inverter generator ,why do you say it isn't for RV . Is it good for Small 24 ft. Travel trailer? 1 small roof air conditioner? And tv outlets few other things ? (Asked March 20, 2021)

We did not say it's not for RV. We said it's not RV-Ready, since it does not have a TT-30R outlet. This does not mean that the unit is not suitable for an RV. You may read our definition of RV-Ready and use our wattage calculator to estimate your appliances power needs.

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