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[wxsig] Trvia comment on 5 dollars a month computer operating cost.

Don Jeerings djeerings at tampabay.rr.com
Sun Jan 14 03:53:47 UTC 2007

Gentlemen.. Just a comment about the computer energy usage per month.

Something to think about.. (trivia) 

I just measured the wattage of 3 different desktop computers (all running weather programs) with the monitors on continuously. "No energy saving"

None of the machines draw less than 82 watts and the monitors (LCD's) draw around 60 watts. The tube type monitors draw around 90 watts. These are the small desktop machines with bare bones equipment installed. 

150 watts (total) is a realistic value for a small desk top machine (not a laptop)

150 watts times 24 hours calculates to  3.6 kilowatt hours per day
3.6 times 30 gives 108 kilowatt hours in a 30 day month
108 KWH times 9 cents / KW gives $9.72  per month.

These are very conservative figures. Remember your computer power supply has at least a 300 watt capability. (at 82 watts, it's just coasting) 

If it was run at 50 % of the power supply rated load, it could cost you (monitor  included) $15.00 per month. Of course this does not generally happen, (but it is possible)  Note the 9 cents a KWH is about average cost in the Florida area. The Lakeland area is near 10. 

It was also interesting to note that the Kilovolt amperes (KVA) was about 2.7 times this figure indicting the switching power supplies are a highly reactive load.

I do not know if it is capacitive or inductive reactance, but should it be capacitive, it helps to improve the power factor of your house load. 

Don Jeerings

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