Apple replacement battery on Macbook Pro not nearly as good as the original battery. Why?

¿Are you running EXACTLT the same MacOS and same versions of Apps as when everything was brand new out of the box?

if not, there really is no way to compare how a new battery is performing in a new environment.

But we can help you get the best possible performance out of your Mac.

By far the easiest way to cause poor performance, instability, overheating and crashing is to install ANY third-party speeder-uppers, Cleaners, Optimizers, Virus scanners, Bit Torrent, or a VPN that you installed yourself. 

¿Are you running anything like that?

Jared Hendler wrote:

Apple replacement battery on Macbook Pro not nearly as good as the original. I have a Macbook Pro (M1) 16" 2021 running latest OS (Tahoe 26.1). Given this laptop is 4 years old, the battery was down to 4 hours off of a full charge with general mail and browsing usage.

It sounds like there was some other problem. Batteries in modern computers don't degrade that fast.

No heavey graphic apps running.

I can assure you that's not true. Tahoe itself very heavily uses the GPU.

I decided to buy a new Apple battery and had the old one replaced. Im now getting about 6-7 hours out of the new battery. While this is an improvement over the old battery, it is substantially less time than what I used to get when the machine was new. Is Apple replacing with used batteries? I would have thought that purchasing a new Apple replacement battery would have gotten me back to the performance like it was a new machine?

Grant Bennet-Alder is correct. The software you're running now isn't the same as what you were running before.

Most likely, you have some background app that is using way too much energy and draining your batter. It doesn't matter what apps you think you're using. The apps that cause these problems run in the background. One problem with modern Apple Silicon computers is that they are extremely fast and very efficient. Back in the Intel days, you would have noticed a problem because your computer sounded like a jet airplane even when you weren't doing anything. But modern Macs can sustain that same level of background load without heavy fan noise or heat. The only way you'll notice is excessive battery drain. Of course you can't think of anything you did to cause it, because you did it 3 years ago. Your MacBook's been cooking for 3 year straight.

Next on the list of resource hogs is Non-native File Sync-ers.  Dropbox, Microsoft OneDrive, Google drive and others are in this category. Since they were ported from that other OS environment, they IGNORE the Mac File System Event Store (that could tell them EXACTLY what folders have changed recently) and instead do a a Brute-force read of all your files, and all the files stored on their drive on the Internet. This punishes the ability to get any data (including speed test data) through their enormous and frivolous file reading and re-reading.

Between constant scanning and constant Internet access, this uses a LOT of resources -- far more than Apple-native File-Syncers like iCloud. Running File-Syncers when not actually needed still consumes a lot of computer resources. You should NOT be launching these at Startup, but instead launch only when needed, and quit when Sync-ing is complete.

Backup-to-the-Web Utilities are also in this category. Your backup should be on a local drive, not on the web. If you question this, just ask.

I decided to buy a new Apple battery...

For clarification, did Apple do the replacement? If not, it's probably not an Apple battery. Your symptoms certainly suggest aftermarket.

When I go to https://selfservicerepair.com/en-US/home , I do not see Macbook Pro batteries offered for sale as parts.