August 27th, 2008 | | By Ken Mankoff
In order to have a website I have to have a computer on 24 hours a day 7 days a week. I try to be aware of my energy usage and in general try to minimize it (except for that one little habit). A webserver uses energy, but in my case it is wind powered.
If you want to calculate the cost of some electronic equipment there are some simple tools you can buy such as a Kill-a-Watt or someday the EnergyHub product line. Rather than buying yet another product, I decide to calculate the costs myself. I got the idea from http://smallnotebook.org.
You need to know two bits of information. The first is the average price per kWh on your electric bill. It should be something around 15 cents. The second is the Amps the electronic device draws. It is printed on the power brick or bottom of every product. Look for this line:
Input: 110-240V ~ 1.5A
In this example the number 1.5 is the Amps. Given those two bits of information, can calculate how much it will cost to run the device. The equation is:
A * V / 1000 * hours * cost
V is 120 in the U.S.
Plug in the numbers. This webserver uses 1.5A, time is 24/7, and NYC electric rate for wind power is 18 c/kWh. The equation becomes:
1.5A * 120V / 1000 * (24h*365d) * 18c = $283.82 per year.
Which is a bit more than I expected. Maybe even enough to end this experiment. (If you can’t read this I’ve turned it off). For comparison, the Roomba uses 0.3A and charges for 3 hour/week. The equation becomes:
0.3 * 120 / 1000 * (3*52) * 0.18 = $1.01 / yr
The old vacuum used 9A, but was used much less (maybe 10 minutes every other week) for a cost of ~$3.
The equations are simple. Figure out which devices cost you the most. If you plug it all in and the numbers don’t make sense, post in the comments below.