As part of a recent review of 24 LCD monitors we undertook for Australian PC User’s July 2009 issue, we also grabbed some extra power consumption measures using full black- and white-level displays to see again if black screens cause a reduction in power consumption.
The 24 review samples came from seven manufacturers from AOC through to Samsung. We used a commercial Australian-made AC power meter to measure the power consumption along with a simple software tool to generate complete black and white screen displays via a PC to each monitor. Brightness levels were set to 100% on each unit.
|Power consumption (Watts) 100% brightness level|
|Monitor||Screen Size (inches)||Black screen||White screen||% reduction|
|Dell C22W Crystal||22||49.1||47||4.28%|
|LG Flatron W2242T||22||43||40.1||6.74%|
|LG Flatron W2261V||22||41.4||40.2||2.90%|
|LG Flatron W2284F||22||45||42.7||5.11%|
|Samsung SyncMaster 2233sw||22||41||39.4||3.90%|
|Samsung SyncMaster 2333sw||23||42.9||40.9||4.66%|
|Samsung SyncMaster 943BW||19||33.6||33.2||1.19%|
As you can see from the results, only two of the 24 monitors (italicised) tested saw a reduction in power consumption going from a white to a black screen. They were Dell’s 2209WA and the Philips 240PW. These both use IPS (in-plane switching) rather than the standard TN (twisted nematic) panel construction. The other 22 monitors all saw a reduction in power consumption going from black to white screen displays.
As far as we’re concerned, this sinks the idea that power consumption can be reduced by using black search engines or backgrounds. The average power consumption drop was nearly one-watt or 3.16% of total power consumption.
Backlight (brightness) reduction gives more
However, whether you have a black or white-screened search engine, background or whatever is almost irrelevant when you compare the power differences here with what can be achieved by simply dropping the backlight (brightness) level. We’ll look at this in more detail shortly, however, as our testing has shown, the backlight accounts for as much as 60% of the overall power consumption of an LCD monitor and that dropping it even just from 100% to 70% can produce up to a 20% drop in power consumption without seriously affecting the screen’s visibility.
What’s equally important is that this drop in consumption through brightness reduction occurs regardless of the type of LCD construction used.
And that makes arguing over black or white LCD screen backgrounds almost pointless.