The 140W power adapter of the Apple MacBook Pro 16 is insufficient, but there is nothing you can do about it
A few months ago, we discussed the power adapter issues affecting the smaller MacBook Pro 14, where the 96-watt adapter proved insufficient. A particular problem was that even a more powerful adapter like Apple’s own 140W model offered no solution, as the device's power intake is capped. This issue also affects Apple’s most powerful mobile device, the MacBook Pro 16 with the M5 Max.
Our comprehensive review revealed that even the 140-watt adapter cannot meet energy demands during sustained heavy workloads, even though the M5 Max is already significantly throttled by thermal constraints. During our stress test with combined CPU and GPU loads, the M5 Max briefly draws up to 114 watts (CPU and GPU only; memory power draw is excluded) before settling at 70 watts - at least in High Power mode (see the chart below). We measured a maximum power draw of 150 watts; it is impossible to feed more power into the MacBook, even when using a more powerful 180-watt (USB-C) adapter. Consequently, the device loses approximately 12 % of its battery charge in one hour under these conditions.
Of course, one could argue that this is an unrealistic, extreme scenario. However, when spending high four-figure sums on a high-performance laptop, one should reasonably expect the power adapter - which, in the EU, must now even be purchased separately - to be adequately rated. A decent power adapter should even have enough headroom to charge the battery to some extent while the system is under heavy load. Apple has always designed its power adapters with very tight margins so this is nothing new, but the reason for limiting the device's maximum power draw remains a mystery to us. Alongside the limited cooling performance, this highlights the age of the MacBook Pro design, as little has changed in this regard for several years. Please see our full review of the MacBook Pro 16 with the M5 Max for more details.
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