Yamaha EF1000iS - 900/1000W Inverter Generator

The Yamaha EF1000iS is a quiet, compact and lightweight inverter generator with a rated wattage of 900 W and a starting wattage of 1000 W.

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Yamaha EF1000iSYamaha EF1000iSYamaha EF1000iS

Get this unit while stocks last, because Yamaha discontinued its production.

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SMALL BUT MIGHTY. Quiet, fuel efficient, and power clean enough to run sensitive electronic equipment all in a portable 28‑lb package.

Zoom on the Yamaha EF1000iS

In summary, the Yamaha EF1000iS is a quiet, compact and lightweight portable inverter generator especially useful for:

  • Camping and tailgating buffs looking to enhance their experience
  • Amateur DIY lovers

The following sections will present you in detail its power characteristics, the different outlets it offers, its overall portability, the extra features it benefits from, and any relevant emission compliance details.

Power & Run Time

The Yamaha EF1000iS in use

The Yamaha EF1000iS

The Yamaha EF1000iS houses a 50 cc Yamaha MZ50 OHV 4-stroke engine, which provides 120V, consumes gasoline and delivers a running wattage of 900W along with a peak wattage of 1000W.

The inverter generator boasts with a low noise rating of 47 dBA (less noisy than bird calls) which earned its spot in our 10 quietest portable generators. Its starting mechanism is based on a simple traditional pull-start mechanism.

This generator features Yamaha's Smart Throttle™. This load-sensing feature automatically adjusts engine speed to match its load in order to offer greater fuel efficiency and noise reduction.

With a fuel capacity of 0.66 gallon, the EF1000iS may run for up to 11.9 hours with a full tank (fuel consumption around 0.06 GPH).

As the EF1000iS produces a clean sine wave, with a <2.5% Total Harmonic Disruption (THD), sensitive electronics may be plugged in the AC outlets safely.


The control panel features the upcoming 2 AC outlets:

Duplex 120V 15A (5-15R)

In addition, it provides 1 DC outlet: there's a 12V 8A receptacle allowing you to easily charge your batteries.


Thanks to its closed inverter generator design (L17.7 x W9.4 x H14.9 in), the Yamaha EF1000iS, is more esthetical than a typical, open frame generator. This modern design aims to provide an ideal power solution to recreational users.

Since the EF1000iS weighs only 27.9 lbs, it can be labeled as a portable lightweight generator. The product’s power can be enjoyed on-the-go, as it can be moved by a single person without trouble. Further convenience is provided by its handle (molded in the case), as it allows you to carry it effortlessly.

Good to know: This unit ranks 5th in our list of the 10 smallest portable generators.


Panel of the Yamaha EF1000iS

The EF1000iS's control panel

Several light indicators serve to show you when the generator is ready, the oil level is too low and the generator is on overload.

Security-wise, this product benefits from an overload protection (circuit breaker) and an automatic low oil shut-off (Oil Watch system), which gives you a complete peace of mind when using it.

Yamaha's Oil Watch warning system gives you an extra peace of mind. This feature enhances long-term durability by preventing engine damage and costly repairs. Once the oil begins to run low, the generator automatically shuts off and cannot be re-started until oil is added.

Accessory-wise, along with the previously mentioned features, the Yamaha EF1000iS is packaged with the standard documentation and an owner's manual (opens in a new tab), helping you start the device right away.


The Yamaha EF1000iS is EPA-approved and CARB-compliant. Therefore, its sale and purchase are permitted in all of the 50 states, including California.

Moreover, it features a spark arrestor, making it usable in forested areas.

Product Videos

The Yamaha EF1000iS versus other generators

The following charts are provided to give you an idea of how some of the key specs of the Yamaha EF1000iS compare to generators of similar power (between 500 and 1500 W).

  • Weight-wise, the Yamaha EF1000iS has only 27.9 lbs, which renders it one of the lighter generators which produce 500 to 1500 rated watts. If you are concerned by weight, one of the champions in the above-mentioned power range is the Sportsman GEN1000i, with a dry weight of just 20.3 pounds.
  • As its lowest possible noise is rated at 47 dBA, this inverter generator qualifies as one of the more quiet of the products of similar power. For those who are looking for a less noisy device, we suggest the Honda EU1000i. With just 42 dBA, it is one of the most quiet devices in this power range.
  • Thanks to an impressive running time of up to 11.9 hours at 25% load, the EF1000iS benefits from a higher run time than many generators of a similar output. If concerned with autonomy, one of the products of a comparable power output, which offers the highest run time, is the Powermate PM2000, boasting with up to 14 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. With an estimated gasoline consumption of 0.06 GPH (gallon per hour) at 25% load, this inverter generator is among the most fuel efficient of the products in the above-mentioned wattage range.
According to our stats, the following comparison is pretty popular: Yamaha EF1000iS vs Honda EU1000i.

Price comparison

As you can see from this interactive chart, when compared to other 500-1500W inverter generators, the Yamaha EF1000iS is on the expensive side of the price range.

While certainly not the cheapest of its kind, purchasing it would most likely also mean enjoying the reliability of a high-end product.

The bottom line

  • Inverter
  • Lightweight (27.9 lbs)
  • Quiet for its power (47 dBA)
  • High run time
  • Fuel efficient
  • On the expensive side
  • No data center
  • No electric start
  • No parallel ports

Do you own the Yamaha EF1000iS and agree (or disagree) with these strengths and weaknesses?

Let us know and write your own review.

Features and Specifications

Parallel capableNo
RV readyNo
Engine50 cc Yamaha MZ50 OHV 4-stroke
Starting systemRecoil
VoltageAC: 120V 60 Hz, DC: 12V
Running watts900 W
Starting watts1000 W
Running amps7.5 amps
Peak amps8.3 amps
Run time @50% loadUnknown
Run time @25% load11.9 h
GFCI outletsNo
Covered outletsNo
Automatic Voltage RegulationInverter
AC outlets1x Duplex 120V 15A (5-15R)
DC outlets1x 12V 8A receptacle
Data centerNo
IndicatorsLow oil, overload and output ready
Fuel tank0.66 gal
Fuel gaugeNo
Weight27.9 lbs
Approx. dimensions (L x W x H)17.7 x 9.4 x 14.9 in
Noise (lower limit)47 dBA
THD< 2.5%
ComplianceCARB, EPA
SecurityLow oil and overload protection
Spark arrestorYes
Accessories includedNo
Warranty3 years

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 Yamaha

With a rich history of over 130 years, the Japanese based Yamaha Corporation, founded in 1887, has tipped its fingers in every industry imaginable, most notably motorcycles, musical instruments and electronics. The company boasts with a wide range of products, including many of the top rated portable generators. However, it has been reported that many of the newer models are made in China, rather than Japan.

Warranty Information

The Yamaha EF1000iS 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 Yamaha generators, please consult Yamaha's warranty policies (opens in a new tab). Alternatively, you can also contact their Customer Support: 1-800-962-7926.

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 homeRice cooker650650
Set of 5 LED light bulbs5555
Total705 W705 W
For campingRV refrigerator180600
DVD player350350
Pair of small speakers4545
Total575 W995 W
For workDrill600900
Bug zapper8080
Total680 W980 W

Couldn't find the right answer for you? Ask your own question.

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Yamaha EF1000iS
3.6 Total Score
2 reviews
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  1. 0.65

    Garbage buy a honda stay away crap

    + PROS:
    • Garbage at dealer for 4th time cant seam to fix it dont buy one
    - CONS:
    • Garbage
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  2. Avatar
    Geoff D Molyneux January 2, 2022 at 11:00 pm

    My Adventures with my Yamaha EF1000IS 2016 Generator.

    I own the Yamaha EF1000IS that I bought in October 2016. When it was not in the shop, it was a very nice generator. But I have had 2 stators replaced. Carburetor Stepper motor was replaced, as it would not idle to full throttle well, and the carburetor was cleaned, this was out of the box. Engine Crankshaft, and connecting rod replaced because the mechanic wrongly diagnosed it, instead of a bad stator. Valve oil seals were replaced as it was burning oil. The last problem was a rod knock noise. I had bought the extended warranty. Yamaha covered all the parts and labor up to the rod knock. This generator has only 400 hours, and has been given an oil change every 100 hours. I have owned this Generator for 5 years. Stators went bad as I was running a 750 Watt heater for a long time. I did not cool down the generator before turning it off. The stator windings are not high temperature rating , so do not like to be heat soaked, melted the insulation enough to kind of fail. Then when I started the generator some time later, the generator started, but went full throttle as the windings completely failed and there was no voltage to run the stepper motor. On the next restart, you can try an pull, and pull the starter rope. There is too much drag on the engine due to shorted windings, and you can not get the generator to start. You can try drill start, spray starting fluid down the carburetor and it will still not start. It has too much load. YOU NOW HAVE A FAILED ALTERNATOR WINDINGS!

    Read you warranty it says to change oil every 6 months, whether or not it has 100 hours. Document all oil changes or you will get warranty denied. Adjust your valves and document that. Last Dealer said that the valve push rods were bent. Maybe using it in -40 Deg F, made valves stick, and then they got hammered with piston. Or valves floated when Stater failed and it went to maximum RPM.

    When the generator is shut off, the Throttle Butterfly valve is fully open. When you start the generator, there are 3 windings on the Alternator. 1 winding for DC charging, 1-3 phase winding for Inverter control voltage, 1-3 phase winding for Inverter output 120VAC. So when my heat soaked generator was started, there was no power for 3 phase Inverter control voltage, so no voltage for Stepper motor to close the throttle. So you have a runaway engine. Yamaha does have an ignition high RPM limit switch, but it will turn off ignition when above that rpm, and turn back on ignition back on. This is a separate control module from the inverter control module.

    I am still waiting for parts to be returned for the Last Rod Knock teardown. First Dealer that worked on engine disabled compression release, trying to figure out how to get the engine to run. So I ran the generator 4 1/2 years without the compression release. You always had to make sure that engine was near TDC before giving a good pull. If not then you would get a good yank backwards on the start rope. The Good thing about not having a compression release, is that your engine will always pump air/fuel through it.

    Some time the start rope wore out. Needed a new starter case, as where rope was guided through the case it had worn and fraying the rope. Not covered under warranty. Dealer on the second stator replacement broke the choke cable. They tried to jury rig it, but again it was not covered under warranty.

    In Canada, the Yamaha EF1000IS has off switches for both DC outlet and 120VAC outlet. These are also breakers. These breakers will not always close in cold weather. So the 120VAC breaker was changed out, again not under warranty. Yamaha said that I was exceeding the rating and it went out of calibration.

    What was nice was the Yamaha was quiet. It had all controls on one side, It had a fuel pump so one could suck from an extended run fuel tank. Was it worth the $1000 Canadian, I spent, No. Did I get my use out of the extended warranty, Yes, but Yamaha still let me down. Other options I got for the Yamaha EF1000IS: The Blue Yamaha EF1000IS case. The case is not the best designed. Hour/RPM meter. Extended run time fuel cap, a magnetic dipstick, an extended oil drain/fill tube. and a 120 Volt crankcase heater hose.

    I always run Mobil Synthetic 10W30 in the Engine. Looking back, I would just use Yamaha Oil, same as what they use in 4 stroke snowmobiles.

    Where the Generator shined, was when it was charging my camper/ or batteries for my CPAP machine. This load was about 25% to 50%. But the generator was not made to run continuously 800 watts or more. It is not designed to run in severe cold weather.

    This engine is tuned for sea level, it needs jets changed to run correctly at 1000 feet elevation. I wish it had Electric Start. I wish that I could replace the Cylinder Sleeve, but it does not have a removable head, so you can not remove the cylinder sleeve. Internet web pages show that one should have got about 1500 hours on the engine, not 400 hours as I have got. Last Dealer (for Rod Knock) says I need new pushrods, new valves, new cylinder, new piston, new connecting rod, new crankshaft. Those parts are more than the cost of a new generator.

    This generator sat on a receiver hitch basket. Running with a 13 liter external fuel tank. Full load would be about 9-11 hours. Just enough time to stop for the night and sleep a full 8 hours. Then during the day, it was asked to heat my car, (cars are only designed operate to -16 Deg C, car are designed to start at -40 Deg C, but car heat will start to decline when driving at 100KPH and it is colder than -16 Deg C.) during the winter travels that I did.

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