LG monitor deep sleep mode
I recently acquired an LG 32UQ750P-W monitor, which like many consumer electronics in the 21st century has piss poor documentation and a lot of mysteriously named settings.
For example, I can set “Response Time” to “Off”, “Normal”, “Fast”, or “Faster”. Why is this an option? The on-screen display explains what this setting does, but not why you’d ever want to change it. Why would you not want the fastest possible response time? (The answer seems to be that faster response times can lead to a messier display - ghosting, distortion, etc. - presumably because the panel spends more time throwing new values at pixels and less time cleaning up?)
Another setting is “Deep Sleep Mode”. The on-screen display says that when Deep Sleep Mode is enabled “power consumption is minimized while the monitor is in standby mode”. Again, why is this an option? Why would anyone not want that? LG’s documentation doesn’t say, but from experimenting a bit with my setup, things were behaving almost as if the monitor was disconnected from my MacBook when in this sleep mode. When waking the display up there were a couple of seconds where macOS acted as if the display had been unplugged, and all open windows had been moved to the MacBook’s built-in display.
When Deep Sleep Mode is disabled this does not happen. I assume in this mode the monitor keeps enough of the electronics powered on to let attached devices know that it’s still there and ready to go at a moment’s notice (“standby mode”?), versus connected but cold-and-dark (“sleep mode”?).
Anyway, macOS sorts itself out within a couple of seconds but it can be annoying hence, presumably, the ability to disable Deep Sleep Mode.
I wanted to know how much power Deep Sleep Mode actually saves so I know whether this annoyance is worth it or not, so I plugged in my Arlec PC222 energy meter to find out and things got weird. With Deep Sleep Mode disabled, after a couple of minutes of the screen being off the monitor’s power draw dropped to about 6W. With Deep Sleep Mode enabled power consumption would never go below about 20W.
Turning Deep Sleep Mode on resulted in more power being used in standby!
(At this point I should note that my M1 MacBook Pro is connected to a CalDigit TS3 Plus Thunderbolt dock, and the monitor is connected to the dock’s DisplayPort port. There’s nothing else plugged in to the monitor.)
I then discovered that if I disconnect or power off either the dock or the MacBook the monitor’s power consumption drops to about 0.5W with Deep Sleep Mode enabled. 6W with Deep Sleep Mode disabled is good but 0.5W is excellent! The 20W I was getting is unacceptable. With my current electricity rate of AUD$0.20669 per kWh, the 14W difference shakes out to AUD$25 a year. The difference between <1W and 20W is over AUD$30 a year. I have no problem putting up with a second of weirdness a couple of times a day if it would save 170kWh!
While the calculator is out, if 10 million Australian households each have one device that is capable of using 0.5W in standby but is actually using 20W, that’s 195MW! That’s output-of-wind-farms territory!
It doesn’t take much to find similar problems being reported online - not exactly regarding power consumption, but about DisplayPort monitors not properly sleeping, or constantly cycling between awake and asleep. Reddit has plenty of posts that specifically mention macOS, and just as many that talk about the CalDigit TS3 Plus. Is this a problem with LG monitors, the CalDigit dock, macOS, or some combination? I don’t know.
What I do know is that I’ve been able to resolve this by connecting the monitor to the CalDigit’s Thunderbolt “out” port using a USB-C-to-DisplayPort cable/adapter, rather than directly to it’s DisplayPort port. I don’t know what that means - it’s now using DisplayPort Alt Mode? Don’t care - everything works in use, and the monitor sips a truly negligible amount of power - less than 1W - when sleeping.
I don’t know anything about DisplayPort, and macOS has it’s fair share of interoperability bugs, but here’s what I think is happening: macOS instructs the display to turn off, which it immediately does. After a couple of minutes, during which time the monitor consumes about 20W, the monitor determines that yep, it’s time to enter deep sleep mode and turns off everything it possibly can, which macOS (or the dock?) incorrectly interprets as a full disconnect. This disconnect causes macOS to reevaluate the devices attached to the host, and upon doing so it sees that the monitor is actually still attached. I’m guessing it then asks the monitor some questions, which causes the monitor to return to it’s “let’s just wait to make sure I can actually enter standby/sleep” mode (drawing 20W), and the cycle starts again.
Why is this only happening when the monitor is connected to the dock’s DisplayPort port? You tell me.