Here's a really simple way to look at it--with 120v you have ONE hot and a neutral--with 240v you have TWO hots--since Volts x Amps = Watts, no matter what...if you have a 1000Watt fixture running at 120V, ONE hot will carry 8.34amps...if you run it at 240V, TWO hots, they will each be 4.17amps, added together, still 8.34amps...the only real reason to run 240v is you can run smaller wires BUT, you need TWO hot wires and a double pole breaker...with 120v ONE hot and a single pole breaker...Volts X Amps will always equal Watts, no savings in electricity since, as has already been pointed out, it's always measured in watts. I know this doesn't really help as far as saving electricity, but it's the truth.