How to fix my Mac mini heating up in sleep mode?

There is no bug - and no problem if Sleep is disabled, as it should be. So do it and be happy (or run along to Reddit).

I'm having exactly the same problem. However, this issue seems to have started after I enabled the Apple Intelligence. I suspect the AI is doing some work in the background. During the "sleep" after display inactive period, my wired mouse light kept on, meaning the mini is actually NOT in sleep mode. After waking up, my M4 mini gets cool again. If I manually put the mini to sleep mode, it does turn off the mouse light, the fan stops, and the case remains cool.

I have a very similar setup and exactly the same encounter of the sleep issue. As I've pointed out before, check the "Low Power Mode" will keep the M4 mini in sleep.

Obviously it's a bug for which Apple has not fixed because not many people noticed this and is not that obvious. However, as a responsible company bragging on environmental credentials, Apple ought to address this issue so that people don't waste unnecessary electricity when the minis are in perceived sleep mode.

Yes, that’s exactly the intention: Sleep is unnecessary - don’t even manual-sleep. Shut for long absences and use the existing settings for regular operation.

I've just tried again with "Prevent" checked and Low Power Mode unchecked. My M4 mini did not go into sleep after a time out period. In fact, it never went into the sleep mode even after 3 hours. It clearly shows that this is a bug, not a faulty operation.

Are you suggesting shutting down an M4 Mac mini or newer Mac nightly? That contradicts Apple’s recommendation, which is to let the Mac sleep unless you'll be away for an extended period. Overnight doesn’t count as a long period. Apple even designed the M4 Mac mini’s power button placement with minimal use in mind. Frequent shutdowns can cause unnecessary wear on components. While powering down is reasonable for weekends or longer absences, daily shutdowns aren’t aligned with Apple’s guidelines. Could you clarify why you recommend this approach?

Early this morning, I noticed a similar issue with my new M4 Mac mini. Despite reaching out to support, the problem remains unresolved. They suggested disconnecting my two external drives (a 1TB SSD and a 2TB HDD), which undermines the purpose of using Time Machine for backups.

What’s puzzling is that the Mac mini stays cool during heavy usage with no fan noise, but after going into sleep mode for 20-60 minutes, it becomes very warm—almost excessively hot. With ample airflow and space around it, I would expect it to stay cooler while idle. I also ran Apple Diagnostics, but no issues were detected.

Any insights or similar experiences?

MobileMeKevin wrote:

Are you suggesting shutting down an M4 Mac mini or newer Mac nightly? That contradicts Apple’s recommendation, which is to let the Mac sleep unless you'll be away for an extended period.

... daily shutdowns aren’t aligned with Apple’s guidelines.

Please tell us where Apple may have documented those guidelines & recommendations. I have never seen them.

Frequent shutdowns can cause unnecessary wear on components.

Urban myth. While there "may" have been an argument for this when traditional hard drives were in play, in this era of SoC's and SSDs there is nothing to wear.

You can get the internet to agree with you on anything 😁 didn't you know that?

You’ve left out important details in your reply, just extracting the sensational stuff and conveniently leaving out helpful suggestions from forum heavyweights on this so-called disk-write “problem”. At the minimum you should link to the thread so people can come to their own opinions.

Give it a break Ian! There’s got to be more to do with the new mini other than staring at the hidden power button, measuring oh-so-hot temps or snapping Activity Monitor every hour for precious aha moments.

Try Reddit or MacRumors if you want more traction, never fails…over here, not so much. All the best!

There is no silent killer and neither Activity Monitor nor unverified 3rd party DriveD are required to be continuously monitored for problems. Not even once a month. Be careful, if people keep leaping to conclusions based on snapshot numbers from Activity Monitor, I won't be surprised if Apple yanks the tool entirely or worse, starts billing $10 for every 10th occurrence :).

Bottom line: All Macs need is a little bit of TLC - not cranking up AM and DD every hour.

Also, excessive disk writes are a fact of external boot life - something Apple does not recommend but some choose anyway. It is dependent on hardware and software configuration which means it's different for every machine sold on the planet. The easiest way to avoid it is to boot internally like 99.99% of users do. Anything else is an invitation for trouble.

Anyway, glad you have found something that works for you. All the best!

So? Refer to your own discussion for what that could or could not mean (@Woodmeister) and my “FWIW” tip, and take it up there if you must. Bottom line: AM is conclusive of nothing when used standalone (hasn’t that been repeated a dozen times already).

Came here because I noticed my m4 mini getting warm too. Turning off sleep is not an option, it should work without using that much energy that the mini gets warm.

I will connect an energy monitor tomorrow and see how much power it draws in sleep mode.

IMO, these extended discussions on Sleep are pointless (also endless) because the problems are all easily avoidable with no compromises.

+1. Based on the reply, it’s a personal opinion being posted as official Apple recommendation, best ignored.