Our Yamaha EF1000iS review provides a summary of its negatives and positives. It attempts to answer the most common questions about its application and operation before ending with a verdict.

Yamaha EF1000iS Inverter Generator: Summary

The Yamaha EF1000iS is a portable inverter generator that offers 1000 surge watts and 900 running watts. It has an inverter that cleans up the power signal, so you can run sensitive electronics like computers and televisions. It has a 50cc, 4-stroke gasoline engine that is CARB compliant.

The negative thing about its rated power of only 900 watts is that you cannot run normal size kitchen appliances. You also need to use only one kitchen appliance at a time, so you do not exceed the maximum rated power. You can run the lights and television at the same time, but when you want to use the microwave or freezer you might need to turn off the television.

Therefore, the Yamaha EF1000iS is too small to provide power for a home or recreational vehicle. It is best for tailgating, camping, and boating.

The Yamaha EF1000iS inverter generator has the following positive things in its favor:

• Perfectly portable power: the generator weighs only 28 pounds.
• Quiet operation: noise levels range between 50 and 60 dBA.
• Fantastic fuel economy thanks to its Smart Throttle system.
• The inverter system provides clean electricity for running a computer or television safely.
• Fuel cock knob makes running the carburetor dry for long term storage much easier.

The Yamaha EF1000iS has a list price (MSRP) of less than $1000, but dealer prices will include other fees that could push the price to over 1000 dollars. As a result, it is an expensive 1000-watt inverter generator. Even so, its high quality and quiet operation might be worth the money (check price on Amazon – paid link).

How portable is the Yamaha EF1000iS inverter generator?

It weighs about 28 pounds (dry weight) and it has a single carry handle on the top, so it is very portable for a 1000-watt inverter generator. Its light weight, small size and overall quietness makes it easy to take along on a camping trip.

What is the fuel tank capacity?

Its fuel tank capacity is 0.66 gallons. It runs on regular unleaded gasoline (pump octane rating of 86 or higher). The unleaded gasoline must not contain more than 10% Ethanol or 5% Methanol. Fuel with greater amounts of Ethanol or Methanol might cause operational problems as well as damage to the rubber and plastic parts of the engine.

The EF1000iS can run for almost 12 hours with a 1/4 power load (225 watts), according to its specifications. It can run for about 3 hours at its rated power of 900 watts. Its Smart Throttle adjusts the engine speed according to the current power load for better fuel economy.

Can it run on propane as a fuel source?

This Yamaha generator is made to run on gasoline only. However, it is possible to convert it to propane with a propane conversion kit, but this might void the warranty.

Is it CARB-compliant?

The Yamaha EF1000iS satisfies the emission ratings of the CARB as well as the EPA and can be bought and used in all 50 states of the USA.

What is the noise level?

Yamaha’s specifications state that its noise level is 47 dBA at 1/4 load and 57 dBA at rated load. That is really quiet for a generator. The low noise levels are due to its glass wool construction, its load sensing engine speed control and its quiet muffler system.

Does the DC outlet protect against overcharging?

The DC receptacle does not protect a battery from overcharging. It only has a DC protector, which protects the DC outlet against power overloads. You need to either calculate how long the battery needs charging or you have to check the electrolyte specific gravity. The battery is fully charged when the gravity is between 1.26 and 1.28.

Can two EF1000iS generators operate in parallel?

The Yamaha EF1000iS does not have parallel connection receptacles on its control panel. Do not try to connect it in parallel with another inverter generator. Take a look at the Yamaha EF2000iS if you want an inverter generator that is capable of parallel operation.

Do you need to add engine oil?

You need to add oil because the generator does not ship with oil in its crankcase to prevent oil leaks during transport. Follow the directions in the Yamaha EF1000iS owner’s manual to fill the crankcase to the upper level. The crankcase takes about 0.34 US quarts of engine oil.

SAE 10W-30 or Yamalube 4 is the standard oil choice, but you may use other oils according to the weather and temperature extremes where the generator is frequently used. An oil funnel will come in handy to prevent oil spills.

Does the Yamaha EF1000iS have an electric starter?

The Yamaha EF1000iS does not have an electric starter, but the recoil start is easy enough to use. You may continue with the starting procedure after the fuel and oil levels are checked. Here are the main points to remember:

• Disconnect any appliances that are connected to the generator.
• Turn off the economy control switch.
• Open the fuel tank air vent knob.
• Turn on the fuel cock knob.
• Turn on the engine switch.
• Pull out the choke knob if the engine is cold.
• Pull the recoil starter until the engine starts.
• Push back the choke knob when the engine is warmed up.

The Yamaha EF1000iS has an automatic warm-up system which increases the engine speed for the first five minutes after a cold start. This warms up the engine quickly and also ensures better power delivery for the first few minutes of operation.

You can stop the engine by first disconnecting all the appliances and then turning off the engine switch. You then close the fuel cock knob. The air vent knob, located on the fuel tank cap, is the last thing to turn off.

What appliances can the Yamaha EF1000iS run?

It can probably run most appliances that operate at less than 1000 watts, or that draw less than about 8 amps. Its inverter technology makes it an ideal power source for a mobile computer, color television or entertainment system. It also works well for lighting up light bulbs.

The EF1000iS can charge a 12-volt automotive battery with the DC outlet and battery charging cables.

You might be able to run a small 3/4″ drill. You might also run a small kitchen appliance such as a 300W blender, 600W refrigerator or 700W microwave oven. However, you can only power a small appliance at a time.

The Yamaha EF1000iS is not made for doing construction work or as a home backup generator. It is at its best for camping or tailgating, but much too small to provide power for your recreational vehicle. It is a bad choice for powering a disc grinder, air conditioner, vacuum cleaner, coffee maker or toaster.

Yamaha EF1000iS Inverter Generator: Verdict

The Yamaha EF1000iS is a quiet, portable, fuel efficient but expensive 1000-watt inverter generator that does not have an electric start button. Convenient for camping and computers, but not macho enough for microwaves and air conditioners (check price on Amazon – paid link).