Thu 19 Jun 2008 16:34
CRT to LCD computer lab replacement: how much of a difference?
We are replacing all the remaining CRTs
in our Computer
Science teaching labs this summer with LCD panels,
a total of 84 units (we replaced about fifty last summer). It's well known
that LCD panels generally use less power when displaying than CRTs do,
but the question is: roughly how much power/carbon emissions will we be
saving through this summer's CRT replacement?
Using a Kill-A-Watt electricity consumption meter, we measured the power consumption of our CRTs (19" Dell P992) and our new LCD panels (19" Samsung 920BM and 22" Samsung 2253BW). When displaying an image, the CRTs draws between 85W and 110W of power, depending on how bright/white the image is. In comparison, the 19" LCD draws 35W of power, and the 22" draws 41W. If we assume an average CRT power draw (when displaying) of 97.5W (the mean), that's a power savings of 62.5W for the 19" LCDs, and 56.5W for the 22". We are replacing 48 CRTs with the 19", and 36 with the 22", for a total power savings of about five kilowatts.
What does this mean over time? If we assume the machines in our labs are displaying for an average of one hour out of eight (our labs are open to students on a seven-day twenty-four hour basis), and if we consider our projected equipment lifetime of four years, this implies about twenty-two thousand kilowatt-hours saved over this period. If we multiply this by a carbon intensity ratio estimate for grid electricity of 0.0453 kgC/kWh, this suggests a savings of about a metric tonne of carbon over the expected lifetime of these LCD panels.