The Apple Watch has never been known for having long battery life. Case in point: Apple never budgeted from the 18-hour battery life estimate until it launched the Apple Watch Ultra. But with watchOS 9, the company has introduced a new Low Power Mode to help extend the time between charges.

Previously, the Apple Watch had a Power Reserve mode, which shut off any functions aside from your ability to tell time and turned your smartwatch into a “dumb” one until you could get it onto a charger. This new mode is different — it’s more like the iPhone’s Low Power Mode. When enabled, you’ll still be able to use your Apple Watch, but certain power-hungry features will be turned off or limited to conserve the battery.

On the Apple Watch, Low Power Mode disables the always-on display and limits sensor readings like background heart rate and blood oxygen monitoring. (You should be aware it also disables irregular heart rhythm notifications, as well as high and low heart rate notifications.)

Low Power Mode also curves LTE and Wi-Fi connectivity. While you’ll still be able to send messages or make calls from your watch, it’ll only fetch notifications about once an hour. As a result, you might miss timely texts and emergency alerts.

However, if you’re in the middle of a workout, don’t worry — heart rate and GPS will be unaffected. Another option that reduces heart rate and GPS sampling is also in the works but is currently unavailable.

This mode is a great option if you’ve got an aging Apple Watch but aren’t looking to upgrade (since battery life is often why people buy new watches). Your mileage may vary, however. Battery life depends heavily on individual usage, and your watch’s battery health is also a factor. You can only squeeze so much out of Low Power Mode if your battery has significantly degraded over the years.

As with the iPhone version, you’ll be automatically prompted to turn on Low Power Mode once your battery power hits 10 percent. But some people, especially those with Ultras, might want to be more intentional in how they use the feature — for example, if they’re participating in an Ironman and need at least 12 hours or so of GPS and activity tracking. On the Ultra, Apple says Low Power Mode can stretch battery life up to 60 hours. (Though, based on our testing, you may get well beyond that.)

First things first — to use Low Power Mode, you’ll need to have watchOS 9. That means this feature is only available for the Apple Watch Series 4 or later. If you have an older watch and you think this feature is worthwhile, you may want to consider upgrading.

In any case, assuming your Watch is equipped with watch OS 9, you can enable the feature in two ways.

The quickest way is through your watch’s Control Center.

You can also turn on Low Power Mode by going to Settings > Battery > Low Power Mode. The benefit of doing it this way is you get extra context into your battery life. Not only can you also see how your battery’s been draining since your last charge, but you can also see what times you may have previously enabled Low Power Mode.

And you can tap Battery Health from this menu to check how much the battery has degraded and enable optimized battery charging settings.