in2minds wrote:
is it possible to double the power output of a petrol generator from
it's rated 240v @ 700w to 240v @ 1400w ?

How would you do that? What conceivable mechanism would create an
additional 700W out of thin air (or zero point fluctuations)? And if it
were possible, why would anyone ever buy/run a 5kW genny when all they
need is a 700W genny + magic device?

--
Grunff