If your iPhone battery life seems like it’s getting worse, that’s because it is, per CNBC.

There’s a simple explanation. If you’ve owned your iPhone — or any phone — for more than a year or so and plugged it in daily, it typically begins to lose its ability to receive a full charge.

The capacity of a battery deteriorates over time, which can be due to the heat from your charger, frequent fast charging or other activities that cause your phone’s temperature to increase, such as gaming, as The Wall Street Journal recently reported.

If your iPhone can’t store more than 80% of a charge, it may be time to get your battery replaced. It’s something you can do at an Apple Store, and it can help you get more life from your iPhone if it’s otherwise in working order.

A battery replacement is free if you have AppleCare+, which costs between $3.99 and $13.49 per month depending on the iPhone model you have. If you don’t have the program, then a new battery costs anywhere from about $69 to $99, depending on your iPhone model.

There’s an easy way to check to see how much capacity your battery has lost. Here’s what to do:

Open Settings.
Choose Battery.
Select Battery Health & Charging.
You’ll see “Maximum Capacity.” This is the measure of battery relative to when you first bought the phone. My iPhone 14 Pro Max from last September, for example, has a capacity of 87%. That means I can’t get Apple’s free battery replacement through the AppleCare+ plan that I pay for. But it explains why my battery life seems like it’s gotten worse.

Take your phone to Apple for a replacement if your phone displays anything less than 80% capacity. It’s a quick and relatively affordable way to improve your iPhone battery life, particularly if you don’t otherwise need a new phone.