A watt is a unit of power. It’s an energy rate, it involves time. It’s 1 joule per second (J/s).
A watt-hour is the amount of energy delivered at a rate of 1 watt over the course of one hour. (J/s x h). And here we get into the trouble already. (The kilowatt-hour is just 1,000 watt-hours, that’s not the source of the trouble.)
Now we have a unit of energy (the watt-hour) that includes the names of a unit of power (watt, which is a rate) and a unit of time (hour) but the watt-hour (and the kilowatt-hour) measures neither of those things. The watt-hour is defined as ((energy / time unit) x different time unit). It’s insane. Even though the time units should cancel out, we keep the ghost of both time units in the name, to no purpose. It works out to just joules; 1 Wh is 3,600 joules. 1 kWh is 3,600,000 joules.
It is exactly analogous to measuring distance in “meter-per-second-minutes,” when you’ve got meters right there.
I don’t understand.
Well, precisely!
A watt is a unit of power. It’s an energy rate, it involves time. It’s 1 joule per second (J/s).
A watt-hour is the amount of energy delivered at a rate of 1 watt over the course of one hour. (J/s x h). And here we get into the trouble already. (The kilowatt-hour is just 1,000 watt-hours, that’s not the source of the trouble.)
Now we have a unit of energy (the watt-hour) that includes the names of a unit of power (watt, which is a rate) and a unit of time (hour) but the watt-hour (and the kilowatt-hour) measures neither of those things. The watt-hour is defined as ((energy / time unit) x different time unit). It’s insane. Even though the time units should cancel out, we keep the ghost of both time units in the name, to no purpose. It works out to just joules; 1 Wh is 3,600 joules. 1 kWh is 3,600,000 joules.
It is exactly analogous to measuring distance in “meter-per-second-minutes,” when you’ve got meters right there.