Picture of an Apple Watch displaying the low power mode settings screen.
It’s a watchOS 9 feature, not a Series 8 one.
Image: Apple

The new low power mode feature in the Apple Watch Series 8 allows it to double its battery life by turning off a few features. Apple said during the presentation that low power mode is coming to the Series 4 and later with watchOS 9.

The company didn't say if the mode would be as effective on older devices as it claims it will be on the Series 8 and Apple Watch Ultra. It is clear that it will be less effective on a few models.

Apple hasn’t put any info about low power mode on its watchOS 9 page yet

Low power mode conserves juice by turning off features like the always on display, workout autostart, heart health notifications, and more, while keeping things like activity tracking and fall detection on. The Series 4 and the SE don't have always-on displays, so turning the screen off won't do much for them.

Apple didn't comment on what types of features it will turn off on watches like the new SE or whether the feature is coming to the budget model at all. The description of Series 4 and later doesn't mention low power mode on the SE's product page.

It is nice to know that there will soon be a way to get at least a little more runtime on your older watch, without having to switch into the ultra-bare-bones power reserve mode. If you want to make your Series 4 last as long as possible, you need to know that Apple will service watch batteries for $79 if you want to.