While investigating our story on whether Blackle actually does save power consumption on computer monitors, we carried out other tests with our commercial AC power meter.

[A small parenthesis here. You’re probably wondering why we have an AC power meter in the first place. I purchased the meter late last year for a story in Australian PC User magazine’s June edition on How to buy Green Gear, which was well received and brought radio interviews around Australia.]

We found that while Blackle caused a small rise in power consumption on LCD monitors, one guaranteed way to drop the power consumption on every monitor, whether it is LCD or CRT, was to drop the refresh rate.

The refresh rate is the speed at which the monitor updates the image on the screen so many times per second. On CRT monitors, this is quite critical because drop the refresh rate too low and you start noticing that annoying flicker.

We found in testing that by using Blackle, power consumption dropped on our 17-inch Mitsubishi DV1770 test monitor from 72.5W to 65.4W. By way of comparison, we retested the same monitor on Google but dropped the refresh rate of the 1024x768-pixel display from 85Hz to 75Hz and found the power consumption dropped accordingly from 72.5W down to 67.9W.

We then tested our 15-inch LG StudioWorks 570LE LCD monitor but instead of a power rise when going from Google to Blackle, we found that we were able to gain a small reduction in power consumption by dropping the refresh rate from 85Hz to 60Hz. In this test, power consumption dropped from 26.4W to 26.2W, certainly not much of a drop, but at least it wasn’t a rise as we found when using Blackle instead of Google.

While refresh rate is critical to comfortable use of CRT monitors, it’s far less critical for everyday use of LCD monitors so if you want to reduce the already low power consumption of your PC LCD monitor, ensure that the refresh rate is as low as possible. Most LCD monitors typically allow 60 or 75Hz, settings allowed for by our other test monitor, an LG L192WS 19-inch widescreen model.

While using Blackle saw a rise in this LCD monitor’s power consumption as well, dropping the refresh rate from 75 to 60Hz saw power consumption on Google fall from 24.9W to 24.5W.

Test Results - Refresh rate changes on Google 

Test Results - Refresh rate changes on Blackle 

From the results, you can actually use less power consumption on an LCD monitor by ensuring the refresh rate is at 60Hz and using Google than by having a higher refresh rate and using Blackle.

The only way we found Blackle to be useful is in CRT power consumption but not to the levels that various Blackle supporters have suggested.

The most useful option is combining Blackle with lower refresh rates where the power consumption can drop from 72.5W down to 56.1W. The problem here however is that you’re running a CRT monitor at 60Hz to get that lower power consumption but certainly at all three refresh rate tests we ran on the CRT monitor, the power consumption reduction by using Blackle was never more than 7W, well below the 15W being claimed.

So if you want to a guaranteed of using less power on your PC monitor, drop the refresh rate down a peg or two. Unlike Blackle, refresh rate reduction will drop your monitor’s power consumption regardless of what type it is.

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