iOS 27 Battery Drain: Why It Happens and What to Check

Faster battery drain in the first days after installing iOS 27 or a point update like iOS 27.2 is usually temporary: the iPhone keeps finishing update tasks in the background. Wait a few days, then use Settings → Battery to see whether one app or setting is still using more power than usual.

Why the battery drops after an update

Apple’s battery drain guide ↗ says you can use the iPhone right after an update, but some tasks related to it continue in the background and can affect battery life and how warm the phone gets. Apple’s advice is to wait a few days and check again. While those tasks run, the Battery screen may show an Insight called Ongoing iOS Update. When it disappears, battery life should return to normal.

If you just moved to a new iPhone, you may see Ongoing Device Setup instead, which means the same thing for setup steps.

Checks to do after a few days

1. Read the Daily Usage chart. Open Settings → Battery. The chart compares today with the last seven days and tells you if you are using more, less or about the same as usual.
2. Look at App and System Activity Usage. Tap View All Battery Usage and then an app. A label like Background Activity, Notifications or Low Signal tells you why it used power.
3. Follow any suggestions. iOS may suggest turning on auto-brightness or auto-lock, or lowering a high brightness level. They appear above the Daily Usage chart.
4. Prefer Wi-Fi and a strong signal. Apple notes that searching for a signal drains the battery. On 5G models, 5G Auto switches to LTE when 5G would not help.
5. Update your apps and iOS. An app that misbehaves after a new iOS often gets a fix within days. Apple’s update guide ↗ shows where to check.

Power Mode settings in iOS 27

On iPhone 15 and later, Low Power Mode sits in Settings → Battery → Power Mode. On iPhone 14 and earlier, it is a switch directly in Settings → Battery, per Apple’s Power Modes guide for iOS 27 ↗. Apple’s battery drain guide adds that it reduces Mail fetch, Background App Refresh and some visual effects. It turns off by itself once the battery charges above 80 percent.

Adaptive Power, on iPhone 15 Pro and later, adjusts performance on days when you use more power than usual and can turn on Low Power Mode at 20 percent. It is on by default on supported models, and you will find it in the same Power Mode screen.

When it is not the update

If drain continues for more than a few days with no Ongoing iOS Update Insight, check your battery’s condition. On iPhone 15 and later, go to Settings → Battery → Battery Health; on iPhone 14 and earlier, Battery Health & Charging. Apple says that if you see Service there, a battery replacement can restore full capacity. Its battery and performance page ↗ explains how capacity changes with age.

Widgets are rarely the main cause, but if you suspect one, our guide to whether animated widgets drain battery shows how to compare usage over a few days. Turning on Low Power Mode can also make widgets refresh less often, as explained in why a widget is not updating.