The Yamaha EF2400iSHC is the heaviest and most powerful of the inverters we evaluate, but owners say it's still nicely compact. It gets consistently high ratings from both reviewers and experts, and is powerful enough to start and run a 13,500-BTU high-efficiency air conditioner.
A powerful inverter. Inverter generators produce AC power just like a conventional generator does. However, it's then converted to DC power, then back to AC again, resulting in a "clean" current that's stable enough to power delicate electronics.
The EF2400iSHC is the most powerful inverter in our report, rated for 2,000 watts and surging up to 2,400 watts. That's enough juice to run essential household appliances during a power outage, and Yamaha claims that high-frequency surge is enough to start most 13,500-BTU high-efficiency RV air conditioners.
The downside of that high-frequency surge is that you can't daisy-chain the EF2400iSHC with another Yamaha to get more wattage. On its own, it can run either an 18-cubic-feet refrigerator or a 5,000-BTU air conditioner -- but not both -- and a 1/3-horsepower sump pump, says a user at Amazon.com. Another says it can charge an RV battery while running a microwave, TV/DVD player and hairdryer.
The standard. The Yamaha EF2400iSHC offers the standard outlets you'd expect on an inverter of this size: two 5-20R plug-ins and a single DC outlet.
Background noise. The EF2400iSHC isn't the quietest inverter in our report -- that honor goes to the Honda EU2000i (*Est. $1,000) by a nose -- but it's close, with a manufacturer-estimated rating of 53 to 60 decibels. That's about as loud as a normal conversation.
A 2006 comparative test published in Camping Life yields a reading of 54 decibels from 20 feet away, and a reviewer posting to ElectricGeneratorsDirect.com says, "You can hear it, but it is just background noise."
Amazon.com users agree, saying "this generator runs and runs, automatically adjusting to changes in load, and does it quietly." An owner of both this model and the Honda EU2000i says the Honda is quieter at idle but the Yamaha is quieter at max load.
An efficient generator. The EF2400iSHC's electric throttle adjusts engine speed to conserve fuel, and Yamaha estimates a runtime of 8.6 hours at quarter load, per 1.6-gallon tank. In its 2006 review, Camping Life tested this inverter under zero load and found that it ran for 11.7 hours, or 7.4 hours per gallon.
Hefty and fairly easy to service. Weighing 75 pounds, the EF2400iSHC isn't exactly feather-light. However, the experts at Camping Life call it "easily portable" and shaped to "fit a fairly small space." They also like its easy to access oil fill, located under a hatch in the front of the generator. However, you must remove an end panel to get at the air filter, and the spark plug is hidden behind yet another panel.
Owners warn that you'll want a long funnel for filling the oil, but praise the Yamaha EF2400iSCH's easy-fill gas tank. They also like its visible fuel gauge, and the fact that all controls are available on just one side of the machine. Reviewers are generally enthusiastic about this model, and we found few consumer complaints. "Put in some gas, pull the handle once or twice and you are good to go," posts one at Amazon.com. The EF2400iSHC is covered by a three-year warranty.
1. Field & Stream
Review Credibility: Very Good Smith evaluates four portable generators, including the Yamaha EF2400iS, based on firsthand experience. He says the Yamaha is one of the quietest generators in this test group.
Review: Portable Power, Bruce W. Smith, Feb. 2007
2. Camping Life Magazine
Review Credibility: Very Good Camping Life magazine evaluates five portable inverter generators suitable for camping and RVing, including the Yamaha EF2400iS, the predecessor to the EF2400iSHC. Based on a team's tests, editors report each model's wattage output, noise level, weight and operating time per tank of gas. They like the EF2400iS's control panel layout and say it's "amazingly quiet" to operate.
Review: Compact Generator Shoot-Out, Editors of Camping Life, June 7, 2006
Review Credibility: Good About a dozen users say at Amazon.com that they're quite pleased with the Yamaha EF2400iSHC, giving it 4.7 stars out of 5.
Review: Yamaha EF2400iSHC Inverter Generator 2,400 Watts, Contributors to Amazon.com, As of November 2012
4. Electric Generators Direct.com
Review Credibility: Fair Here the Yamaha EF2400iSHC gets a perfect 5-star average rating from nearly 50 owners. One says he has a 13,500-BTU air conditioner on his boat, and the EF2400iSHC "has no problem starting and running this AC." He calls it a "fantastic generator."
Review: Yamaha EF2400iSHC - 2000 Watt Inverter Generator, Contributors to ElectricGeneratorsDirect.com, As of November 2012