They are both energy. Watts are Joules/seconds so if you're dividing by time and then multiplying by time (an hour in this case) they obviously cancel out and y

They are both energy. Watts are Joules/seconds so if you're dividing by time and then multiplying by time (an hour in this case) they obviously cancel out and you end up back with just Joules. Specifically 1 Watt-hour==3600 Joules.