A rule of thumb for remembering whether you want to say "power" or "energy".

If you could replace "power" with "horsepower", you're on the right track!

If you could say "gallons of gas" instead of "power", you mean energy!

wHrs is energy (and kind of a dumb unit. Watts is already joules per second, so you're saying (joules/second)*hours. It would make more sense to just say joules.

You are correct, 500W for 1 hour (.5kWh) would completely counter the breathing of one crew member for that 1 hour.