A reasonable rule
of thumb is you get what you pay for. Pure sine wave units require some expensive parts
and thus are expensive. Modified comes down to how much the square wave is modified. That takes components which equals money
equals poor sine wave quality and expensive equal better. Having said that, there is little that won't run of a cheapy these days. I had a cheap
Asian unit 3000W cont, 6000W peak and everything I had ran off it.
A microwave oven
is the biggest draw. It requires 3x the cont. run current
to start the magnatron running.