My MacBook Pro battery is draining when in sleep mode

Check battery health: Go to System Preferences > Battery and check the battery health status. If it says it needs service, it may need to be replaced.

TeejT wrote:

It still shouldn’t be draining from 100 to 0 overnight while it’s asleep and it’s that which I’m trying to figure out.

And hopefully someone will help you figure that out.

If it's less than 90 days since Apple replaced the battery, you should contact them and let them know you're still having issues.

Sorry for the misunderstanding; I’m used to answering iPhone and iPad battery questions.

How are you defining “asleep” - what are the exact steps you are taking? And what are your settings in System Settings/Battery?

Lawrence Finch wrote:

Even more reason to leave it plugged in. A MacBook will run on battery only for 10 to 12 hours.

I do agree that the OP may have an issue if the MacBook is draining like that with the lid closed. But all the more reason to leave it plugged in overnight at least until the issue is resolved.

Even more reason to leave it plugged in. A MacBook will run on battery only for 10 to 12 hours.

For some reason it isn’t going to sleep, so that is what you have to look for. Do you have mechanical or SSD storage?

Are you saying it's draining while it's plugged in? Or are you not plugging it in? If not, why not? If you have a power outlet available, you should be plugging it in. The OS will manage the battery charging automatically.

TeejT wrote:

Yes, because it is already charged fully and I see no point in keeping it plugged in if it’s fully charged and being put to sleep for the night.

Because it's how you help train optimized charging. And there's no reason not to.

The other reason to leave it plugged in overnight is that allows the phone to be powered from outside power, letting the battery rest, and thus extending its useful life.

Normally an iPhone will drain around 25% overnight, depending on your settings, how many email and text updates you get, how many Notifications for apps it receives. Smartphones are never doing nothing; there’s always something going on and using power. And even if you have none of those, the phone still maintains a “conversation” with your cellular network so the network can find you when there is an incoming call or text. Network traffic uses a lot of energy.

If you are concerned about the 100% drop look for the app that is using the most energy. There are two things that use energy when the phone is asleep: apps that update/receive notifications, and cellular network handshaking.

You can see the apps and their energy usage in Settings/Battery.

If the above isn’t long enough, here’s the really long answer→When to charge your iPhone or iPad | Communities

Lawrence Finch wrote:

The other reason to leave it plugged in overnight is that allows the phone to be powered from outside power, letting the battery rest, and thus extending its useful life.

Normally an iPhone will drain around 25% overnight, depending on your settings, how many email and text updates you get, how many Notifications for apps it receives. Smartphones are never doing nothing; there’s always something going on and using power. And even if you have none of those, the phone still maintains a “conversation” with your cellular network so the network can find you when there is an incoming call or text. Network traffic uses a lot of energy.

If you are concerned about the 100% drop look for the app that is using the most energy. There are two things that use energy when the phone is asleep: apps that update/receive notifications, and cellular network handshaking.

You can see the apps and their energy usage in Settings/Battery.

If the above isn’t long enough, here’s the really long answer→When to charge your iPhone or iPad | Communities

(Pssst - it's a Mac)