Unit analysis
A long-overdue post about a very common error.
One reader (who I hope does not mind me quoting him anonymously) wrote:
I replied:I was confused by your dislike of the term kh/w and baffled by your assertion that it is a meaningless term....
You seem to be asserting that the term KWH is meaningless and not a defined amount.
You've got a relatively common confusion of two different things. Let me see if I can clear this up.
A kilowatt-hour is a kilowatt TIMES an hour. A kilowatt in turn is 1000 watts, there are 3600 seconds in an hour, and a watt is a joule per second; a kilowatt-hour is thus 3.6 million joules (the basic unit of energy in the MKS units system). Kilowatt-hour is abbreviated "kWh".
kW/h would be a kilowatt DIVIDED BY an hour. This is not a unit of energy, it's a rate of change of power; in most contexts, it's simply wrong. Some people write "kilowatts per hour" and it's just as wrong [it's just as wrong because it's the same thing].
¶ 11/10/2005 11:20:00 AM
