What's great is 5w and a wire tossed up into a tree also works. Not as well, but it works.
I was laughing during the DX contest last weekend when I got a guy in Chile on 40w like he was calling my phone. One minute later another guy in Chile with 1000w and we had to repeat things and squint to complete the QSO. I'm sure there were many variables at play, but a meager station did at least as well as one of those mega stations. Stations were trying to reach the US so it's not like Station B would have been pointed at Europe (on purpose anyway).