High GPU Power Consumption While Using External Monitor in MacBook Pro 16-inch

Link to the much bigger thread which was started back in November, and has at least one IT guy trying to work through the issues on multiple work systems with Apple.

https://discussions.apple.com/thread/250878229?page=1

wegster wrote:

We may need a new thread simply titled - $$$ MBP16 degrades performance and longevity due to needlessly high GPU power consumption and see if it gets any attention. :(

Doing that here won't do any good. This is an end user forum and the handful of Apple Mods are so busy keeping the wheels on this massive forum that they do not have time to read and report threads to Engineering. I've been here almost 20 years--trust me on this.

The best action has already been posted: the feedback link. That gets information to Apple employees working in development and things get done. This is the link for MacBook Pro issues:

Feedback - MacBook Pro - Apple

I can confirm that my MacBook Pro 16" connected via either an LG 4k 27" or the LG 5K2K 34", has the following behaviour:

• clam-shell mode: fans at about 1700-1900 RPM, as normal, low noise
• lid open (it does not matter if display brightness on MBP is zero, or if mirror displays or extend desktop mode): fans about 3200-3300 RPM, noisy

So yeah, I don't mind the clam-shell mode but we loose the True Tone on the external monitor in this way, which is a pity.

Temps etc. for my above post as we seemingly can't edit once posted.. :-/

MBP 16 32 GB RAM, 2TB SSD, 8 GB AMD.

Single external 38" UQ QHD+ 3840x1600 attached. Makes no difference in cable attachments, with or without dock, 18W+ minimum. Wanted to add a second, but instead am stuck with this.

I am also experiencing this problem, connecting a monitor will raise the machine temp by 20c+ when idle. When doing video calls the temp can increase significantly, something which does not happen when the monitor is not connected.

MacBook Pro (16-inch, 2019)

2.3 GHz 8-Core Intel Core i9

16 GB 2667 MHz DDR4

AMD Radeon Pro 5500M 4 GB

Intel UHD Graphics 630 1536 MB

LG 34WK95U-W

Resolution: 6720 x 2834

UI Looks like: 3360 x 1417 @ 60 Hz

Framebuffer Depth: 30-Bit Color (ARGB2101010)

Mirror: Off

Online: Yes

Connection Type: Thunderbolt/DisplayPort

Am using the same cable that came with the monitor and which was working with the previous gen MBP.

I have the same problem.

MacBook Pro (16-inch, 2019)

2,6 GHz 6-Core Intel Core i7

16 GB 2667 MHz DDR4

AMD Radeon Pro 5300M 4 GB

Intel UHD Graphics 630 1536 MB

Samsung S32D850T

Resolution: 2560x1440 60 Hz

Connection Type: Thunderbolt/DisplayPort

I also tried the official Apple HDMI adapter with the same result.

Same issue.

MBP 16 - 32GB RAM, 2TB SSD, 8GB AMD.

Numerous cables, with and without a dock - zero difference - always 18W+ with a single LG external display, so will heat soak sooner. 5W in clamshell mode.

It took Apple YEARS before they built a system I was willing to replace my higher end 2015 MBP with, and now this. This is not appropriate for a 'highest end MacBook PRO.'

I've been fighting this since Thanksgiving weekend, same issue, power consumption goes up over 19W when the lid is open and connected to an external monitor.

Since some on these forums had success with reducing the power load through going with a monitor that can accommodate higher refresh rates, I bought a new monitor with 1440P/144 Hz capabilities. Connected to my MBP 16 with the lid open (via USB-C cable to DP 1.2), I get the same result; 19.5W.

Tried several different refresh rates and resolutions, same result.

Have you tried using a display port cable? I've heard that helps a lot.

Nevermind just saw you were using a display port, did you have any other displays connected?

This is very sad I was planning to get some display port cables to get around this issue..

I only have one monitor plugged in other than the internal screen - I am likely going to have to run in clamshell mode until they fix it. No Touch ID, no Touch Bar, none of the features that makes it a MacBook Pro.

I am reporting to Apple again today.

I have the same problem, my second Mac. This appears to be a software bug in macOS or AMD's drivers. Plugging in an external monitor at certain resolutions will cause the AMD GPU to draw 18-20W constantly, no matter what it's doing. This causes the total system draw to increase from ~10W to ~30W. 

My specs:

2.3 GHz 8-Core Intel Core i9

16 GB 2667 MHz DDR4

Intel UHD Graphics 630 1536 MB

1 TB Flash Storage

I just got my 16 inch MacBook Pro and have the same issue.

This is my setup:

MacBook Pro (16 inch, 2019)

2,4 GHz 8-Core Intel Core i9

32 GB 2667 MHz DDR4

AMD Radeon Pro 5500M 4 GB

Intel UHD Graphics 630 1536 MB

with

Kensington TB3 Dock

with

LG 32 inch 4k display via Display Port

My tests results match what others where saying:

The MacBook 16 inch is staying cool when I use it only with internal monitor, or if I use my external 4k monitor with MacBook in Clamshell mode (display closed).

The graphics card is struggling, if I use both an external 4k monitor and the MacBook’s internal monitor and use high resolutions, e.g. 3360 x 1890 (HiDPI)

When I choose 3360 x 1890 in low DPI for the external display, the graphics card relaxes and the system cools down.

Even with HiDPI resolution the load of the system isn’t high and it’s only at around 65°C, but the fans still go crazy at around 4000 - 5000 rpm.

To summarize: The performance is very nice, but the fans go crazy when the graphics card needs to power an external 4k monitor together with the internal monitor.

I reported it to Apple and will report it to AMD, too.

I think the only solution if a firmware update from Apple, that's it. We could see it as part of one of the next macOS updates, we can only hope. Maybe in 10.15.5, which is going to come soon, you never know.