Power Requirements for an iMac? And Mac mini?

I’d clamp a meter onto a representative candidate, and measure.

But I’m also not loading up branch circuits. Not if I can avoid it. And if I was, I’d prefer to add branch circuits.

Per the official data, iMac 2025 models draw 100W and 105W max, for the two- and four-port models, respectively.

I’d wonder about the 143W power supply rating and whether that is provisioning for connected devices also drawing power, which is a whole ‘nother discussion here.

Meter. Clamp. Measure. Add some margin. Etc.

MrHoffman wrote:

iMac 24” unusually doesn’t list wattage, but does ship with a 143W power adapter.

We have to delve into Apple's Product Environmental Report to obtain any meaningful data regarding its actual power consumption. Last page.

Even that is of limited value because it describes power consumption "at idle" — an operational state they define, but that definition implies it's not being used.

So the answer to OP's question is that we can certainly connect a room full of iMacs to a typical 15A branch circuit, but actively using more than a dozen or so simultaneously is likely to trip a 15A breaker. This assumes the 143W power adapter is producing 100% of its rated output current and power at its specified efficiencies.

Maybe running a Geekbench stress test will get it to that limit; I haven't tried.

Mac mini M4 maximum continuous power 155W

Mac Studio (2025) maximum continuous power 480W

iMac 24” unusually doesn’t list wattage, but does ship with a 143W power adapter.

Measured values are often lower, as most folks aren’t buying the fully-specified configuration.

Measure your config for your limit.

For local power and cooling limits, and for environmental requirements and limits, check with an electrician and HVAC tech.

Using a device called a Kill-A-Watt, I measured:

27" iMac with internal 1GB HDD ... 155w steady draw, idle

27" iMac with internal 1TB SSD ... 85w-160w under various light loads. Appears to center around 125w.

I wouldn't risk putting more than 4-5 on a single 15A circuit nor would I put them on a single power strip or surge suppressor. Make sure you also consider all peripherals and any resource-heavy apps you may use. In my case, all my computers are on 20A branch circuits.

Even if X amount of systems can run on a 15A circuit, that does not mean they can all be powered on at once since that can blow the circuit breaker.

Plus you also have to consider the power requirements of a Display for those systems that do not have a built-in display.

MrHoffman wrote:

… Per the official data, iMac 2025 models draw…

Correction: iMac 2024 models, as there is presently no iMac 2025 model.

👍

That's a much more useful report.