Replace your iPhone battery when it no longer holds a full day of normal use, when the phone shuts down unexpectedly at 20 percent or higher, or when the battery health in Settings drops below 80 percent.

Your iPhone battery degrades with every charge cycle. After about 500 full charge cycles — roughly one to two years of normal use — most iPhone batteries retain only 80 percent of their original capacity. At that point, you will notice the phone drains faster, struggles through a full day, or powers off without warning even when the battery percentage shows charge remaining.

The exact timing depends on how you use your phone and how you charge it. If you charge to 100 percent daily and let the battery drop to zero regularly, you will see degradation sooner. If you keep the phone plugged in constantly or let it sit unused for months, the battery ages differently. Apple's own data shows that most users notice a real difference between years one and three.

Key Takeaways

  • Check your battery health in Settings > Battery > Battery Health & Charging; if it shows below 80 percent, replacement will noticeably improve performance.
  • Unexpected shutdowns at 20 percent battery or higher are a sign the battery can no longer deliver the power your phone demands, even if the percentage looks normal.
  • Battery replacement costs between $50 and $100 depending on your iPhone model and whether you go to Apple or a third-party repair shop.
  • Replacing the battery is usually cheaper and faster than buying a new phone if your iPhone is otherwise working well.

How to check your battery health right now

Open Settings, tap Battery, then tap Battery Health & Charging. You will see a percentage labeled "Maximum Capacity" — this is how much charge your battery can hold compared to when it was new. You will also see a "Condition" line that says either "Normal", "Service Recommended", or "Service Not Available".

If the maximum capacity is 80 percent or higher and the condition says "Normal", your battery is still healthy. If it is between 70 and 79 percent, you are in the range where you may start noticing slower performance or faster drain. Below 70 percent, Apple recommends service. The "Service Recommended" label appears when Apple detects the battery cannot deliver peak power reliably anymore.

Unexpected shutdowns mean the battery is failing

If your iPhone powers off suddenly when the battery percentage shows 20 percent, 30 percent, or even higher, the battery is no longer able to supply the power your phone needs in that moment. This is different from normal drain. The percentage is a guess based on voltage; when the battery ages, it cannot maintain voltage under load, so the phone shuts down to protect itself.

This happens even if the battery health percentage looks acceptable, because health is measured under ideal conditions. Real-world use — running multiple apps, using the camera, or playing video — demands more power than the test does. Once you see this pattern, replacement will stop the shutdowns when ready.

Battery degradation happens faster with certain habits

Charging your phone to 100 percent every single day and letting it drop to zero wears the battery faster than keeping it between 20 and 80 percent. Leaving your iPhone in a hot car or using it while it is charging also accelerates degradation. Storing the phone fully charged for months without use can damage the battery permanently.

If you have been charging aggressively for two years, your battery may be at 70 percent health already. If you have been careful — using optimized battery charging, avoiding heat, and not letting it fully drain — you might still be at 85 percent after three years. Check your own battery health to see where you stand rather than guessing based on age alone.

What replacement costs and where to get it done

Apple charges $69 for an iPhone 15 or 14 battery, $79 for an iPhone 13 or 12, and $89 for older models. The work takes one to two hours at an Apple Store if you have an appointment, or you can mail the phone in and get it back in about a week. AppleCare+ covers battery replacement at no cost if your plan is active.

Third-party repair shops like Best Buy's Geek Squad or independent local repair shops often charge $40 to $60 for the same work. The trade-off is that non-Apple repairs may not come with the same warranty, and some shops use non-original batteries that may not last as long. If your phone is still under warranty or covered by AppleCare+, Apple service is usually the safer choice.

Replacement is worth it if your iPhone is otherwise working well

If your phone is two to four years old, the screen is not cracked, and the only problem is battery life, replacement is almost always cheaper than a new phone. A new iPhone costs $800 to $1,200. A battery replacement costs $70 to $90. Even if you need a screen repair at the same time, you are still spending less than half the price of a new device.

The only reason to skip battery replacement is if your phone is already failing in other ways — the screen is damaged, the charging port is broken, or the logic board is failing. In those cases, the cost of fixing everything adds up, and a new phone may make more sense. But if the battery is the only issue, replacement extends the life of a working phone by another year or two.

Frequently Asked Questions

Can I replace the battery myself?

You can buy a replacement battery and tools online, but opening an iPhone requires heat, precision, and knowledge of where the adhesive and connectors are. One slip can damage the screen, logic board, or battery itself — and a damaged battery can catch fire. Unless you have done this before, professional replacement is safer and often costs less than the tools and replacement battery combined.

Will a new battery make my old iPhone feel like new?

A new battery will restore battery life and stop unexpected shutdowns, but it will not speed up the processor or improve the camera. If your phone feels slow, that is usually because the storage is full or the operating system is running many background tasks, not because the battery is old. A battery replacement will make the phone last longer per charge, not run faster.

How long does a replacement battery last?

A new battery will reach 80 percent health in roughly 500 charge cycles again, which is typically one to two years depending on how much you charge. If you use the same charging habits that wore out the first battery, the second one will degrade at the same rate. Changing to optimized battery charging and avoiding heat can extend the life of the replacement.

Should I replace the battery before it gets really bad?

If your battery health is at 85 percent and your phone still lasts a full day, you can wait. If it is at 75 percent and you are noticing drain by evening, replacement now will save you the frustration of unexpected shutdowns later. There is no penalty for waiting, but there is also no benefit — the battery will not recover, only get worse.