Some users of Apple’s newest MacBook Pros aren’t happy with their battery life. Though the Apple Support Communities forums, Twitter, and other message boards will necessarily amplify complaints, it does seem fairly common for users of the Touch Bar model in particular to see battery life that falls short of Apple’s 10-hour estimates for Web browsing and movie playback.

Apple called extra attention to the issue this week in the newest macOS Sierra update, not by fixing it but by removing the “time remaining” estimate that some users had been sharing to demonstrate the battery problems they were having. The accuracy of that battery estimate aside—and it was always more useful as a “rate of battery drain” indicator than as an actual time estimate—it looks like a superficial solution designed to solve a PR problem rather than an earnest effort to fix anything.

Anecdotal reports since the 10.12.2 update hit have suggested that the update could improve battery life, but I don’t think this is the case—Apple told us repeatedly and emphatically that it had taken no specific steps to improve MacBook Pro battery life in this update. According to Apple’s data, the company said the batteries appeared to be performing as intended.

Given the extra (and well-earned) attention, let's break this battery situation down. How is Apple arriving at its battery life figures, and why might yours be falling short? If you’re coming from an older MacBook Pro, why might you be seeing lower battery life than before? But most importantly, what—if anything—can you try to do to fix it?

Apple’s estimates

We can't say exactly what tests Apple is using, nor can we recreate them with complete accuracy. But here’s the full spiel from the MacBook Pro’s tech specs page—Apple generally gets these figures by testing basic configurations with Core i5 CPUs and the minimum amount of RAM (8GB for 13-inch laptops, 16GB for 15-inchers).

The wireless web test measures battery life by wirelessly browsing 25 popular websites with display brightness set to 12 clicks from bottom or 75 percent. The iTunes movie playback test measures battery life by playing back HD 1080p content with display brightness set to 12 clicks from bottom or 75 percent. The standby test measures battery life by allowing a system, connected to a wireless network and signed in to an iCloud account, to enter standby mode with Safari and Mail applications launched and all system settings left at default. Battery life varies by use and configuration.

Apple’s browsing test doesn’t sound too far off from our own, though Apple sets its screen brightness just a little lower than our standard 200 nits (around 80 or 85 percent on the slider). And while this sort of test is useful for comparing laptops relative to one another, it’s not necessarily representative of real-world use. It doesn’t account for multitasking or screen switching; there aren’t particularly intensive tasks running in the background; and assuming the laptop is running some kind of script and not actually taking user input (as is the case with our test), the Touch Bar may go idle and shut itself off. It’s not that Apple is fibbing about its battery life figures, it’s just that the test isn’t really reflective of what a lot of “pros” are doing with these laptops. What’s using all that power, then?

Sapped by setup

These laptops are brand new, and many people have only had them for a few days. As Apple noted to us when we asked about the battery issues, those first days can be particularly punishing for your battery, especially if you’ve got a lot of data on your drive or in iCloud.

Apple’s Spotlight indexing service crawls through all of that content to make it easier to search through later, and iCloud syncing for iCloud Drive, the iCloud Photo Library or Photo Stream features, and other features can also make for a lot of uploading and downloading. Battery life in the first day or two may not necessarily be representative of normal battery life once everything has settled down.

This could also help to explain some of those reports that battery life has improved since the 10.12.2 update landed. It could be that the update’s installation coincided with the end of those first-time Spotlight and iCloud operations.

What you’re doing with the laptop really, really matters

More than ever, the new Pros’ battery life will be determined by what you’re using the machine for. That has always been the case, but it’s different primarily because of three things: smaller batteries, a more power efficient screen, Intel’s recent CPU stagnation, and the 15-inch models’ mandatory dedicated GPU.

Compared to last year’s models, the Touch Bar MacBook Pros lose quite a bit of battery capacity. The 13-inch model drops from 74.9 WHr to 49.2 WHr and the 15-inch model falls from 99.5 WHr to 76 WHr. That’s a 34 percent and 24 percent reduction in capacity, respectively.

If you reduce the size of the battery and you don’t want to totally tank battery life, you need to find power savings elsewhere. The CPU and GPU and the display are the biggest possible areas of savings since they’re going to draw more power than components elsewhere in the system, and Apple says that it has reduced the power consumption of the screen by about 30 percent.

The problem is that this isn’t the same as a system-wide 30 percent power reduction, which is roughly what you’d need to make up for the capacity loss in both systems. The issue for Apple is that 2016’s Intel Skylake processors use around the same amount of power as 2015’s Broadwell processors used in the last 13-inch Pro and only a little bit less than 2013’s Haswell CPUs that were still used in the 15-inch Pro.

The 2013/2014, 2015, and 2016 Pros all use processors that have the same thermal design power, or TDP: 28W for the 13-inch models and 45W for the 15-inch models. These numbers aren’t meant to measure power draw (they’re used primarily to denote how much cooling capacity a given chip should have to perform optimally), but they give a good ballpark estimate. For slightly more precise figures, here are the power draw numbers for three generations of Intel NUC desktops using comparable chips with 15W TDPs.

Activity Haswell NUC Broadwell NUC Skylake NUC Off/Hibernated 0.5W 0.5W 0.4W Sleep mode 1.1W 1.0W 1.1W Idle at desktop (display off) 6.4W 6.7W 7.1W Watching YouTube in Chrome 9.0W 9.1W 10.2W Running GFXBench Manhattan benchmark (peak) 38.0W 37.2W 34.1W Running Prime95 CPU torture test 29.7W 31.8W 31.0W

Sometimes the newer chips consume a tiny bit less power than the older ones, and sometimes they use a little bit more, but they’re broadly comparable. The power savings that enable those smaller batteries aren’t really coming from the processor.

Also, keep in mind how 2013’s Haswell CPUs managed to improve battery life so noticeably compared to 2012’s Ivy Bridge CPUs. Starting in Haswell, CPUs can jump between their active and idle states more quickly, allowing the processor to spend more time idling. If keeping track, that's three significant factors impacting the situation:

The new laptops have smaller batteries than the old ones.

Intel’s CPUs are responsible for a higher percentage of total system power use, since they consume about as much power now as they did one or two or three years ago.

The less idle processor time you have, the less Intel’s recent power optimizations can help you.

All of this means, in short, that what you’re doing with your computer has more to do with your real-world battery life than before. It’s why there’s such a huge difference between our Wi-Fi browsing tests and our heavier WebGL tests, and a smaller battery means you’re going to notice it more in the new Pros.