Wednesday, April 15, 2009

How Did California Determine CRT TV Energy Use ?

The California Energy Commission's TV energy use FAQ on their proposed regulations says:
How much wattage do different types (CRT - cathode ray tube, liquid crystal display - LCD, plasma) of televisions use?
It's hard to compare CRTs to LCDs and plasmas. On average, CRTs use 0.23-watts per square inch of the screen, LCDs use 0.27-watts per square inch, and plasmas use 0.36-watts per square inch. Below are comparisons of the "average size" of each type of television and the wattage they use, and a comparison of wattage used by a 42-inch LCD versus a 42-inch plasma.
There are few direct-view CRTs that are as large as the big LCDs and plasma TVs. A 40-inch (diagonal), direct-view HDTV is the industry's largest direct-view cathode ray tube. It uses 280 watts while in operation and only one watt in stand-by mode.

So how did the CA Energy Commission arrive at 0.23 watts per square inch for CRT televisions? I'm still looking. According to the staff report, that power usage information came from the Pacific Gas & Electric (PG&E) study "Analysis of Standards Options for Televisions: Revised Proposal" which was put together to help the California Energy Commission. Reading the PG&E report, however, shows ... zilch on CRT TV energy use! Separately, I did find one private "Pro Bono Statistics" blog, based tests they describe as less than rigorous, of two Sony WEGA CRT TVs that shows 0.23 W/in² and 0.29 W/in²; and notes that CRT televisions are far more efficient that CRT monitors! NRDC's presentation has some data too, but again uses less than rigorous methods.

CNET has tested more than 100 television models, using their own lab method, but they have no CRT data because they have only tested non-CRT televisions televisions :( In their chart, rear-projection was the energy efficiency winner at around 0.13 W/in² (sort by "Per sq in.") and rear-projection is not even listed in the CA FAQ.

In Nov 2008, Energy Star v3.0 added TV ratings in a technology agnostic fashion:

CRT TVs have such a small market share now that the California Energy Commission probably feels it's not worth digging into, however, if CRTs really are so energy efficient, perhaps we should look at them again!