A watt wouldn't make any sense. A watt needs a time unit to be converted to joules because a watt is a measure of power, while a joule is a measure of energy.

A watt wouldn't make any sense. A watt needs a time unit to be converted to joules because a watt is a measure of power, while a joule is a measure of energy. Think of it like speed and distance: A watt is a RATE of energy use, just like speed (e.g., miles per hour) is a RATE of travel. A joule is a total amount of energy, just like distance (e.g., miles) is a total amount of travel. If you're traveling 60 mph but you don't specify for how long... You won't know how far you went, how much gas you used, etc.