Putting up Christmas lights this year was a serious beating. I kept blowing breakers due to the amount of lights I put up in response to my wife’s request for ‘more lights!’ It seems like every year things get bigger and bigger (like most things in America – trucks, combo meals, taxes, and the deficit). The problem is there is only so much power in convenient areas of my house and those locations don’t have enough power to run my lights because they are shared with things inside the house. My front porch outlet ties in with my garage outlets so every time we open up the garage door, the breaker blows and the Christmas lights on the front of the house go out. I got tired of resetting breakers and I ended up running 2x 20amp 110v dedicated feeds to my roof and to the front yard.
As I was putting the lights up, I found myself doing power calculations in my head. I multiplied the amount of lights I put up by the watts each bulb consumes to get the total watts. Then I took the total watts and put it into this conversion tool (http://www.mhi-inc.com/Converter/watt_calculator.htm) to calculate what they use in a Kilowatt hour. I have timers setup to turn on the lights from 6pm to 11pm (CST) so that is 5 hours a day. I plan to run them from December 8th through January 3rd which is 27 days totaling 135 hours of run time. Take the Kilowatt hour the lights generate times the hours of operation and you get the total Kilowatt hours used for the holiday season. I was then curious how much this was going to cost me (I am a cheap bastard) so I took out my electric bill (TXU, yes I am paying too much) and took what they charge me for a Kilowatt hour and got the dollar figure it costs to run the lights. I was surprised it is not as much as I thought considering how much light my house now generates. It lights up the neighborhood like the Griswold’s house in Christmas Vacation <http://www.imdb.com/title/tt0097958/> . I would not be surprised if you can now see my house from the space shuttle.
I don’t envy Softlayer’s operation guys because they do these types of power calculations (albeit on a much grander scale) on a daily basis. They have to figure out what types of servers with different components (CPU, drives, memory, raid cards) can go into a single rack to insure that power strips are not blown. Some people don’t understand that you can’t just fill a rack up with 44 1U (or 22 2U) servers and turn them on. You have to carefully plan down to the watt how many of each type of server can go into a rack without overloading circuits. You also have to take into account customer upgrades and make sure there is enough headroom for power spikes upon booting. The math involved in my yearly Christmas light escapade made my head hurt; I can’t imagine what Robert and Brad go though. Hats go off to them. My head would have exploded by now….
Here is the math (rounded):
15 ½ stands of C9 Christmas lights each with 25 bulbs = 385 bulbs
385 7 watt bulbs = 2695 watts
2695 watts = 2.695 Kilowatt hours (from http://www.mhi-inc.com/Converter/watt_calculator.htm)
2.695 Kilowatt hours multiplied by (5 hours a day for 27 days = 135) = 364 total Kilowatt hours
364 total Kilowatt hours times $0.12 = $44
So lighting my house for one month actually uses significantly more electricity than running a server in a SoftLayer data center for the same period of time.