Hello David , Good question!
I extracted the following comments from an article provided by a long cruiser Bob Brooks - Catamaran "Cathouse" I posted the article somewhere a long time ago - it must be in the archives.
* Electronic inverters are not all the same, there are two basic types
on the market.
* SQUARE WAVE INVERTERS are by far the cheapest, most rugged, efficient,
and repairable. On the down side, this type is not well voltage
regulated nor is it's operating frequency very stable but many modern AC
powered devices just don't care. For example: power tools, sewing
machines with brush motors (not the processor controlled types),
computers, TVs and other multi-volt electronic equipment will operate
Square wave inverters Will NOT work with induction or
capacitor start motors like household fans and refrigerators (motors
with brushes, like your power tools, are ok). Also on the down side this
type generates HF radio noise, has higher idle (no load) current and is
not load sensing to automatically turn on, you must manually switch to
power up AC when you need it.
* The MODIFIED SINE WAVE type inverter is a sophisticated, expensive,
and irreparable (the mfrs. will not provide a schematic and active
components have the identification erased) piece of equipment that is
easily zapped by near-miss lightning. The advantages of most of this
type is that it will sense you plugging-in or turning on your appliance
to power itself up and provide accurate regulated frequency and voltage.
* Combined INVERTER/CHARGERS for marina queens, a lot of money for that
charger function and they radiate HF radio noise that screws up your
radio and everybody else's on your dock.
* The Heart inverters, 120V and 240V
120V inverter and the 240V inverter powers only the microwave, blender,
and power tools.
All of our other appliances are now efficient direct 12V operating. The last
to go were the 19" TV, the computer monitor, and the amplified speakers.
All replaced with a Samsung 15" LCD video/TV/PC monitor, does it all for
only 2.2amps at 12V and a picture quality that must be seen to believe.
The LCD in your laptop fades only a few degrees off axis, this thing is
still viewable 80 degrees off axis.
* You won't find square wave inverters at West Marine. Try looking for
USA made TRIPP LITE on the net. Or, if you're in Thailand, SPECTRUM has
a line of VERY affordable square wave inverters.