Your iPhone battery degrades over time, and you'll notice it most when it won't hold a charge through a normal day

iPhone batteries are designed to retain 80 percent of their original capacity after 500 full charge cycles—that's roughly one to two years of normal use. After that point, the battery still works, but it holds less charge with each cycle. You don't have to replace it the moment it hits 80 percent capacity, but you should start paying attention to how your phone behaves. If you're charging twice a day, your phone shuts down unexpectedly at 20 percent battery, or it can't make it through a workday without a charge, replacement is worth considering.

Apple's Battery Health feature, built into every iPhone running iOS 11.3 or later, tells you exactly where your battery stands. Open Settings, tap Battery, then Battery Health & Charging. The number shown under "Maximum Capacity" is what matters—that's the percentage of your battery's original charge it can still hold. If it's below 80 percent and you're noticing real-world problems, replacement makes sense. If it's above 80 percent but your phone still drains fast, the issue may be something else entirely.

Key Takeaways

  • Check your battery's maximum capacity in Settings > Battery > Battery Health & Charging; if it's below 80 percent and your phone drains quickly during normal use, replacement is worth considering.
  • Unexpected shutdowns at 20 or 30 percent battery, even when the phone feels cool, are a sign the battery can no longer deliver the power your phone needs.
  • Apple's official battery replacement costs between $69 and $99 depending on your iPhone model, and takes one to two hours at an Apple Store or authorized repair shop.
  • Third-party repair shops often charge less but may use non-Apple batteries, which can affect performance and may not show accurate health data in Settings.
  • If your iPhone is still under warranty or covered by AppleCare+, battery replacement may be free or significantly discounted.

Unexpected shutdowns are the clearest sign your battery needs replacement

If your iPhone powers off suddenly when the battery percentage shows 20, 30, or even 40 percent, your battery is failing. This happens because the battery can no longer deliver the burst of power your phone needs during peak use—when the camera is running, the processor is working hard, or you're using multiple apps at once. The phone shuts down to protect itself, not because it's actually out of power.

This is different from normal battery drain. A healthy battery that's just small (like in an older iPhone) will last all day if you use it lightly, but drain faster under heavy use. A failing battery will shut down your phone even during light use, and the shutdown point gets lower each week. If this is happening to you, replacement will restore normal behavior when ready.

Performance slowdowns often come from battery problems, not age

Starting with iOS 12, Apple added a feature that slows down your iPhone's processor when the battery can't deliver enough power. This was meant to prevent unexpected shutdowns, but it also makes your phone feel sluggish—apps take longer to open, scrolling stutters, and games lag. If your phone has slowed down noticeably and your battery health is below 80 percent, the slowdown is likely battery-related.

You can check whether this slowdown is active by going to Settings > Battery > Battery Health & Charging and looking for a message about "Peak Performance Capability." If it says your phone's performance has been reduced, replacing the battery will restore normal speed. If the message isn't there but your phone still feels slow, the slowdown is probably caused by something else—too many background apps, storage nearly full, or an older processor that's straightforward not as fast as newer models.

What to expect from an Apple Store or authorized repair

Apple's official battery replacement costs $69 for most iPhone models, though some newer models like the iPhone 15 Pro Max cost $99. The repair takes one to two hours at an Apple Store, or longer at some authorized repair shops depending on how busy they are. You can book an appointment online through Apple's website or the Apple Support app, or walk in and ask about same-day service if you're willing to wait.

When you bring your phone in, the technician will run a diagnostic to confirm the battery is the problem, then replace it with a genuine Apple battery. Your data stays on the phone—they don't erase it. After replacement, your Battery Health will show 100 percent maximum capacity, and you'll get a fresh 500-cycle warranty on the new battery. If your phone is still under the original one-year warranty or covered by AppleCare+, the replacement may be free.

Third-party repair shops cost less but come with trade-offs

Independent repair shops often charge $30 to $50 for battery replacement, significantly less than Apple. The work is usually fast—sometimes same-day—and many shops are convenient to your home or office. However, third-party batteries are not always the same quality as Apple's original parts. A cheaper battery may not hold a charge as long, may not show accurate health data in your Settings, and may not carry a warranty if something goes wrong.

If you choose a third-party shop, ask whether they use original Apple batteries or aftermarket replacements. Some shops stock both and let you choose. Original batteries cost more but behave exactly like Apple's. Aftermarket batteries are cheaper but may not integrate fully with iOS—your Battery Health percentage might not update correctly, or the phone might not recognize the battery at all.

When to replace your battery before it fails

You don't have to wait for your phone to shut down unexpectedly. If your battery health is between 70 and 80 percent and you're noticing that you need to charge more often than you used to, replacement now will save you the frustration of sudden shutdowns later. This is especially worth doing if you rely on your phone for work, navigation, or emergencies.

If your battery health is above 80 percent but your phone still drains fast, the problem is probably not the battery itself. Check whether a specific app is using too much power by going to Settings > Battery > Battery Usage. If one app is using 30 percent or more of your battery, that app may have a bug or may be running in the background when you're not using it. Uninstalling it or updating it often solves the problem without needing a battery replacement.

How to extend your battery's life before replacement becomes necessary

Battery degradation is inevitable, but you can slow it down. Keep your phone between 20 and 80 percent charged as much as possible—charging to 100 percent every day and letting it drain to zero stresses the battery more than moderate charging. Enable Optimized Battery Charging in Settings > Battery > Battery Health & Charging; this feature learns when you usually charge your phone and slows charging to 80 percent until you need it, reducing wear.

Heat also degrades batteries faster. Avoid leaving your phone in direct sunlight, in a hot car, or running demanding apps (like games or video recording) for long periods without a break. If your phone gets hot during normal use, it may have a hardware problem or a runaway app—check Battery Usage to see what's consuming power, and consider a repair if the heat persists.

Frequently Asked Questions

How long does an iPhone battery last before it needs replacement?

Most iPhone batteries last one to three years before they degrade noticeably, depending on how often you charge them and how you use the phone. Apple designs them to retain 80 percent capacity after 500 full charge cycles. If you charge your phone every day, you'll hit 500 cycles in roughly one to two years.

Is it worth replacing the battery or should I just buy a new phone?

If your phone is less than three years old and works well otherwise, battery replacement is almost always cheaper than a new phone and will make your current phone feel new again. If your phone is older, has other hardware problems, or the battery replacement cost is close to what you'd pay for a used replacement phone, a new phone might make more sense financially.

Can I replace my iPhone battery myself?

iPhones are difficult to open safely without damaging the screen or other components. Apple and authorized shops have the right tools and training. If you try it yourself and damage something, repair costs will be much higher than a professional battery replacement. It's not recommended unless you have experience with phone repair.

Will replacing my battery fix my phone if it's running slowly?

Only if the slowdown is caused by battery problems. Check your Battery Health first—if it's below 80 percent and you see a message about reduced performance, replacement will help. If your battery health is above 80 percent, the slowdown is caused by something else, and replacement won't fix it.

What happens to my data when I get a battery replacement?

Your data stays on the phone. Battery replacement doesn't erase anything. The technician removes the old battery and installs a new one while your phone remains intact. You'll have all your apps, photos, and settings exactly as they were before the repair.