Stopping Dell P2715Q monitor flickers with MacBook Retina 12" (2015)

I have recently purchased both a Dell 4K display (P2715Q) and a new Macbook (Retina, 12", 2015). According to Apple's website, the MacBook should be capable of driving the display at full resolution at 30 Hz, when connected over HDMI (via Apple's own USB-C to HDMI adapter), https://support.apple.com/en-us/HT202856. While the display is detected correctly and I can select up to the full 3840 x 2160 (though it defaults to 1920 x 1080) pixel settings, the Dell display continually flickers, going blank for a fraction of second every few seconds. This behavior persists regardless of the choice of scaling.

Has anyone else encountered this issue (or not) with this setup (or other 4K display)? Any strategy to resolve this issue?

Things I've tried:

• Doing an NVRAM reset on the Mac (https://support.apple.com/en-us/HT204063, as suggested by Apple's help desk) and
• a Factory Reset in the Dell monitor menu options (the only suggestion from Dell's help desk)

both of these appear to reduce or sometimes stop the flickering for a few hours, but it returns by the end of the day (or if the Mac is left on over night). Having to reset NVRAM every day isn't a great experience...

Edit the problem persists both while the laptop is in Clamshell mode (with the lid closed) or open as an additional monitor.

This may be good or bad news deepening on how you look at it, but it’s the Dell 4K display, not your Mac. Both Dell model numbers 2715Q and 2815Q are notorious for this kind of flickering when used with MacBooks. If you search around on Amazon and other sites you will find similar complaints.

We purchased 4 of the Dell 4K P2715Q monitors where I work, and we returned ALL of them in the end because they exhibited this exact flickering behavior (as well as the inability to properly run at 60Hz).

It didn’t matter if we connected different types of Macs, or used different connectors. If we tried to drive these monitors at full resolution we saw this problem.

Dell told us the same thing when we called support (and we have the good support where I work), and we still never succeeded in making them work.

If you do find a solution with your Mac that makes this monitor work properly I will be happy to learn about it.

EDIT: For the benefit of anyone coming to this answer and wondering about other’s who’ve seen the same problem. Check out Apple’s forum posts reporting the same problems with the P2715Q.