How much energy does a modern LCD display use?

September 6, 2012 10:28 PM

If you have a recent 18" to 20" size LCD monitor and a kill-a-watt watt meter, can you please plug it into the watt meter and tell me how much power it's actually drawing?

I am trying to calculate the cumulative Wh load for a small-ish desktop PC setup to be semi permanently installed on a boat. This will include an Intel DN2800 series mini-itx Atom motherboard that consumes a max of about 10.5 watts. I have found various 19" size LCD monitors that claim power consumption of around 25W. How close to a real world figure is this?

For reference I have an old Dell 1907FP 19" 1280x1024 monitor here that is using 32W (as measured by a kill-a-watt) at 100% brightness. Therefore I am hoping that the claimed figure of 25W for a modern 19" to 20" monitor is actually pessimistic on the part of the manufacturer.

posted by thewalrus to Technology (7 answers total)

Check your MeMail.
posted by The Master and Margarita Mix at 10:43 PM on September 6, 2012

Data point: The Dell 1907FP is 32W-33W at max, or 19W to 20W at 25% brightness. I'm hoping to find data from a post-2011 generation LED backlit model of similar size.
posted by thewalrus at 10:59 PM on September 6, 2012

In my experience (PhD student studying energy consumption of office electronics) 25W for a newer 20" monitor is about right and could maybe be on the high side, but not by much. I find manufacturer specs for on power tend to be pretty accurate. I don't have data at hand to confirm this, though.
posted by PercussivePaul at 12:42 AM on September 7, 2012

None in that range, but two that are close. Here's what I have:

Brand	Model	Diag. inches	On	Claimed	Sleep
Dell	E173FPc	17		28	35	0
Dell	E177FPf	17		21.7	40	0.7
I-INC	iH282	27		81	85	0.5
HP	2710m	27		84	90	0.5

"On" and "Sleep" are in Watts. Note that in the specs for the first one (the oldest I have), the watts are described as "<=".
posted by jwells at 7:28 AM on September 7, 2012

You may already know this, but by far the biggest power draw for an LCD is the backlight. Setting the brightness down low will consume 50% or less of the power of the brightness at full.
posted by Nelson at 7:57 AM on September 7, 2012

Dell P2411H 24" LED backlit

Published specs:
Voltage Required: 100 to 240 VAC/50 or 60 Hz + 3 Hz/1.5 A (Max.)
Power Consumption Operational: 27 W (typical)/ 50 W (maximum)*
Power Consumption Stand by / Sleep: Less than 0.15W
*Maximum power consumption with max luminance, Dell Soundbar, and USB active

Actual numbers (no soundbar or USB):
Max at 100% brightness: 22W
Typical at 70% brightness: 17W
25% brightness: 10W
0% brightness: 7W

At 0% the backlight is still on and the monitor is entirely usable, though not at a level that would be comfortable for an extended period of time.
posted by Max Camber at 8:50 AM on September 7, 2012

Thanks Max, that's exactly the sort of data I was looking for. I had a strong hunch that 19"-20" LED backlit displays would be sub 25W. If that Dell 24" is 22W at absolute max brightness. a 20" LED unit (Samsung) will probably be around 20W worst case....
posted by thewalrus at 2:28 PM on September 7, 2012