After some two years or so of the GMC generator, these thoughts may prove useful.
These are marketed under several brands, including the ubiquitous GMC sold by Bunnings. The so-called $98 one is rated at 500 watts, the dearer one at 650, with 850 peak.
I've tested both the AC and DC output with a digital multimeter. WIth no load, the AC fluctuates around the desired 230V mark, quite erratically, but within acceptable tolerances for my needs. Some switchmode power supplies don't mind that, otherw do.
We use the AC to run a 650 watt toaster oven, which has several heat settings. On the lower, warm-up setting the generator hums along, but speeds up considerably to max out at its rated 650 watts.
I also run small wattage power tools: 500 watt router, 500 watt drill, 150 watt orbital sander. It handles them with ease without any appreciable speeding up of the motor.
I've experimented with an old 10" Philips TV, and the generator produced wavy vertical lines. Not recommended.
The DC seems to fluctuate around 12.8 volts. That is insufficient to charge a battery. Placing the voltmeter in series with a 12v car battery, the input has never been greater than 2 amps. The supplied cable is extremely short, and pretty useless unless you a) place the generator right next to your in situ batter and kill yourself on carbon monoxide, or b) remove the battery and place it next to the generator in the open.
Until recently it always started on first or second pull. Now it requires removing the spark plug and cleaning it to start.
The unit tends to condense oil from the exhaust, which drips down one leg and can leave a stain on whatever it's sitting on.
Lately, a tiny leak has developed from under the petrol filter (which connects to the carburettor). That could be dangerous.
It weighs 22 kg, same as the Honda eu201. Quite easy to handle with one arm. But the Honda outputs 1600 watts, compared to GMC's 650. I have heard both and I would say they are just as quiet. Yes, we like the quietness of the GMC.
Petrol consumption is very light, but needs to be mixed 2-stroke.
To output 50hz, the motor must run at 3000 RPM. But with no load, it's much less, and quieter still.
The manual suggests storing empty -- but the only way to do that is to turn it upside down and let petrol spill everywhere. There should be a tap on the tank.
SUMMARY: For running small voltage insensitive power
tools and appliances, the GMC 850, with 2-year warranty, is very economical to buy and run.
--Inspired