The New iMac’s Power Adapter Has a Secret

Apple’s new iMac has a power adapter that’s far more capable than the latest 24-inch model requires.

The new 24-inch iMac has a 143-watt power adapter. That’s strange because it has Apple’s M1 silicon, a chip so efficient that Apple managed to stuff it in the new iPad Pro. Which begs the question: what is the extra power for? The answer hints at future iMac models expected in the fall or winter of 2021.

"Apple is likely planning to reuse this power adapter in future 24-inch iMacs with better chips over the next couple of years, which makes total sense," Vadim Yuryev, co-host of the Max Tech YouTube channel, said in a Twitter Direct Message to Lifewire. 

Napkin Math

Yuryev has earned a reputation for quality coverage of Apple rumors, though not because of his first-hand leaks. Instead, Yuryev draws together credible leaks and adds context by comparing leaks to existing Apple products.

His iMac “final specs confirmed” video, published the day before the Spring Loaded event, correctly guessed Apple would announce a new 24-inch, 4.5K iMac using only the existing Apple M1 chip in two different base configurations.

His post-launch coverage was quick to point out the new iMac’s surprisingly capable 143-watt power adapter. Apple’s official specifications state the most powerful Mac mini M1 consumes no more than 39 watts of power. That’s far less than the new iMac’s power adapter can deliver.

Some spare power is consumed by components not found in the Mac mini. "You can account for a very small amount of it in the speakers and webcam," said Yuryev.

"The only other factor is pass-through charging if you plug in a device or phone." Pass-through charging is limited to 15 watts on existing M1 Macs. In total, you can estimate these factors at no more than 20 watts.

What about the display? Yuryev thinks it will use around 30 watts of power. LG’s 24UD58-B, the only 24-inch 4K monitor currently available, lists an "operating power consumption" of 40 watts. Let’s assume the worst and pencil in the iMac’s 24-inch 4.5K display at 40 watts. 

Adding these factors together puts the new 24-inch iMac’s maximum power consumption at 99 watts.

That leaves 44 watts of power the new iMac doesn’t need. 

Twice the Performance Without Twice the Power

There’s even more performance headroom than appears at first glance. "The 8-core M1 CPU took around 13 watts peak in our testing," said Yuryev. "The 8-core GPU took 5.6 watts peak." You’ll notice these figures are far less than the Mac mini M1’s maximum power consumption.

Its maximum power consumption includes far more than the CPU and GPU. The Mac mini’s speakers, wireless connectivity, RAM, and storage all draw power. Even the M1 chip has several co-processors, such as the Neural Engine.

That’s why Yuryev’s estimated figures for CPU and GPU power draw, which add up to less than 19 watts, are far lower than the Mac mini M1’s maximum power consumption.

This tells us future M1 chips with increased core counts need less power than napkin math suggests. A theoretical M1X chip with double the current model’s CPU and GPU core count won’t double the power consumption of Macs that use it.

What Will Apple Do With All That Power?

It’s clear Apple can increase the new 24-inch iMac’s performance without upgrading the power adapter. What does that tell us about Apple’s future plans? 

"They can probably double the CPU and GPU cores and power a discrete GPU on top and still be under 143 watts," said Yuryev. "However, a larger display could end up using a lot of power, especially if it uses mini-LED tech, so maybe they will have to have a more powerful power supply."

Apple’s environmental report states the 32-inch Pro Display XDR consumes less than 38 watts at SDR brightness, which hits up to 500 nits. However, it consumes up to 105 watts at XDR brightness, which peaks at 1,600 nits. 

The 143-watt power adapter could handle a new 27-inch iMac M1 with a performance upgrade if its display has a peak brightness of 500 nits like the new 24-inch iMac. If the 27-inch iMac M1 upgrades to an XDR display, however, the 143-watt power adapter seems inadequate. 

In any case, the current power adapter all but confirms future 24-inch iMac performance upgrades. Apple could easily swap in a 12-core or 16-core version of the M1 chip without replacing the new 24-inch iMac’s power adapter. That’s good news for iMac fans holding out for more powerful versions of the M1 chip.