I have an old secondary monitor with poor energy efficiency and am considering replacing it. One LCD monitor I found is listed with an EU energy rating claiming an SDR on-mode power demand of just 3.3 W, along with 0.3 W when off and 0.2 W in standby. For comparison, my main monitor uses about 32 W and my current secondary uses around 35 W. Can a monitor really consume roughly one-tenth as much power, or does "on-mode power demand" mean something different? The listing appears to use the official EU certification figures, so I'm unsure whether the number is genuine. The product manual also says it needs a 5 V, 2.4 A power supply, which suggests a maximum supply capacity of about 12 W.
2 Answers
It may be possible, but the measurement conditions matter a lot. A small LCD running at extremely low brightness—perhaps only around 30 nits—could get close to 3 W. At a more typical brightness of roughly 200 nits, the same display would more likely use somewhere around 30–50 W, depending on its size and electronics. The rating probably reflects a standardized test setting rather than normal everyday brightness.
Treat the marketplace listing cautiously and check the manufacturer’s documentation. A required 5 V, 2.4 A adapter means the monitor may need up to about 12 W, although that is the adapter’s capacity and not necessarily its normal consumption. A claimed 3.3 W could be real under favorable test conditions, but it would leave very little power for a bright, full-size monitor.
That makes sense. I’m mainly concerned that the official figure may have been measured with the brightness set so low that it isn’t representative of normal use.