GENMAX GM12500iET review: our full analysis

Power output: running and starting watts

The GENMAX GM12500iET delivers 10,500 W continuously and up to 12,500 W for a few seconds to start motors on gasoline. On propane, the manufacturer rates it at 9,500 running watts (11,500 W starting), 10% less. On natural gas: 8,500 running watts (10,000 W starting). It handles 14 of the 14 loads on our typical list one at a time; add up the running watts of everything you run together, plus the extra starting watts of the biggest motor. As an inverter, it produces clean power suited to laptops, TVs and furnace control boards.

Typical figures; check the label of your own appliances. One load at a time: add up everything you run together.

GENMAX GM12500iET10,500 running W · Tri fuel inverter · typical price over $2,500 Check best price

Runtime and fuel

The fuel tank holds 6.9 gallons of gasoline. At half load, it runs about 7 hr 20 min on a full tank. That is about 0.95 gallon per hour at half load, or 23 gallons for a full day of running, so plan your fuel storage for a multi-day outage. On propane, a standard 20 lb tank holds about 4.7 gallons of LP; propane does not go stale, which makes it the easiest fuel to stock.

62 dB(A): how loud is it?

The manufacturer rates the GENMAX GM12500iET at 62 dB(A), usually measured at 23 feet (7 m) and a light load. That is about the level of a conversation or a dishwasher: acceptable at a campground.

Outlets and home connection

Its panel offers 2 × 120 V household outlets (5-20R), L5-30R 30 A 120 V twist-lock, 14-50R 50 A 120/240 V, USB ports, 12 V DC outlet. The 14-50R outlet supplies 120/240 V, which is what a manual transfer switch or an interlock kit with a power inlet box connects to, installed by a licensed electrician. Never backfeed the house through a wall outlet.

Start type, CO shutoff and warranty

It starts with a remote key fob or the electric push-button, with a recoil cord as backup. A CO shutoff sensor stops the engine if carbon monoxide builds up around it; it does not replace distance (20 feet from the house) and CO alarms indoors. It is listed as EPA compliant; check California availability if you live there. The warranty runs 3 years (residential use).

Typical price over $2,500: good value per watt?

Relative to its running watts, the GENMAX GM12500iET scores 5.1/10 on value: a high price per watt, which its other strengths may justify. Inverters always cost more per watt than open frames: compare it with other inverters. Generator prices on Amazon move a lot, especially before hurricane season: check the current price before you buy.

GENMAX GM12500iET10,500 running W · Tri fuel inverter · typical price over $2,500 Check best price