(Mega)watt hour is a common unit of energy in electrical power because it's convenient. (For example, my power company reports my power usage in kWh (~100 kWh f

(Mega)watt hour is a common unit of energy in electrical power because it's convenient. (For example, my power company reports my power usage in kWh (~100 kWh for my family currently)) A 60-watt lightbulb will use 60 watt hours over an hour.