Units of Power

"Nearly all men can stand adversity, but if you want to test a man's character, give him power." -Abraham Lincoln

I've posted before on the importance of understanding where you are using the most power.  How can you effectively decrease energy consumption if you don't know where it's being used?


Unfortunately, this is complicated by the absurd and antiquated ways in which we quantify power:  electricity in watts, heating in BTUs per hour, cooling in tons, driving in horsepower.  With all of these different units, it's difficult to compare them and understand which appliances consume the most power.  There are historical reasons for these units, but it would be much simpler if all power was given in kilowatts (kw) and all energy was given in kilowatt-hours (kwh).


At the end of the article, I give the relevant conversions, but here is the typical power consumed by various items, all in kilowatts, so you can directly compare.

Keep in mind that these are units of power.  To convert to energy (which is relevant for CO2 consumption and your costs), you need to multiply these numbers by the amount of time (in hours) that you are using each.  For example, a microwave uses a hefty 1.5 kw, but only for a few minutes.  If your CFL light bulb is on for three hours, it uses about the same amount of energy as that microwave did heating up your dinner.  


Notice the huge range in numbers there.  Your air conditioner and car use massive amounts of energy in small amounts of time.  A car on the freeway is using the same amount of power as 650 CFL light bulbs.  This is the first place to start when cutting your energy usage.  If you're cranking the AC or commuting an hour each way to work, turning off a light bulb for an extra hour doesn't make a dent in your total energy consumption.  


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Here are the equivalents to 1 kilowatt:

3,412     BTU/hour
1.34       horsepower
0.284     tons