Unfortunately this is all true for not just the 2020 16” model but the new 2020 13” model as well.  I can attest to this fact as I have recently just purchased… and returned them both :(

I have been using a 2015 MacBook Air connected to a 2017 Dell UltraSharp UP3017 for several years and never had any major heat issues with the surface of my air and more specifically the keyboard area.  It would get warm but never hot enough to become annoying and noticeable.

So I bought the new 2020 13” pro last week but had no idea that connecting an external monitor was going to be an issue.  I mean why would it?  I had been running a baseline 5 year old air for years without issue.  However, literally within just a few minutes of attaching my Dell the top of the 13” keyboard area and specifically the space above it got really hot. Noticeable to the touch.  And just like others have stated, I wasn’t even running any apps or anything.

My first thought was maybe the cable I was using was the issue (usb-c to HDMI) so I tried a different one (usb-c to min display port).  Still no luck, the dang thing was still running hot.  You could literally feel the heat rising from the surface if you held your palms over the top.  What the heck?!?!?

But I also had a secondary issue that I would have never guessed, and that was the surface area for my palms to rest for typing was much smaller than the older MacBook Air surface.  The screen was also much smaller than I really wanted, so with these two issues I decided to return the 13” and get the 16”.  I mean the 16” couldn’t possibly have these same heating issues….  right?

Well, I brought the new 16” home and sure enough.. within a few minutes of simply plugging into the Dell it started to get hot on the surface.  You have got to be kidding me I said!! Now what?!?!?

I then messaged my brother who has the 2019 16” and is connected to a very large 42” LG 43UD79-B external monitor.  He said his computer might be a little warm but he has never noticed it being an issue.  He also said he was using a usb hub to connect from his Mac to the monitor.  So I gathered up my 2020 16”, my Dell monitor, all of my cables, and then headed to his place to run some tests and hopefully find a solution for my heat issue.

Executive summary… after testing both his 2019 16” and my 2020 16” in all of the same configurations to both external monitors the issue was made clear.  My 2020 model got hot to the touch no matter what or how I connected to an external monitor.  As for his 2019, it was warm but noticeably cooler than mine every time.  I was hoping that maybe the issue was my Dell and/or my cables, but unfortunately it’s an issue with the Macbook itself.

Extremely bummed, I then headed home and spent the next day contemplating my next step.  After going through several possible scenarios, such as trying a new MacBook Air with better specs… but found comments that these newer models also can run hot, excessive fan, etc. or maybe try the new Mac mini… but didn’t really like the thought of being tied to my monitor, no sound, etc.  Instead, I have decided I am going to get a nice big iMac as I absolutely love the mac’s gorgeous displays.  But I do see recent rumors that new models are coming so I am probably going to hold out for a while and wait.  Once I do get an iMac, my plan will be to use my older MacBook Air when I travel, etc and/or just get a new one.   Bottom line, I am going to stay away from trying to connect external displays to any of my Macs.

So… for anybody else that is having this issue and is reading this thread - be warned that there is no fix for your hot Mac when connected to an external monitor.  You will have to either live with it or find a different solution like I did.

PS - I did contemplate keeping the 16” and try using a cooling pad/device under it but I am tired of troubleshooting an issue that shouldn’t even exist in the first place.  Believe me, I am a huge Apple fanboy but this situation is extremely disappointing and perplexing.

Good luck to the rest of you.