Why is my Mac battery draining so fast and how can I fix it?

Sounds pretty likely that you've run up the recharge cycles over the years and it may be time for a new battery.

The generally accepted rule of thumb is to connect the MacBook to the AC unless you absolutely cannot. This helps keep the recharge cycles low and reduce battery aging.

Check the condition of your Mac laptop’s battery - Apple Support

Mac Repair and Service - Apple Support

The best advice for getting the most from your battery:

• Plug in when using the computer near available power.

• Use on battery when ac is unavailable.

• Don’t subject the computer and battery to extreme temperatures.

• Let the OS and charging circuits manage the charging.

• Try not to allow the battery to discharge deeply regularly before plugging in. Yes, it may happen from time to time, just don't make it a habit.

• Don't obsess over battery life and/or health.  

Here is Apple's guidance on the subject.

Batteries - Maximizing Performance - Apple Support

About battery health management in Mac laptops - Apple Support 

Other factors I've observed here and in my own Macs that result in shortened battery runtime:

— Google Chrome: a known resource hog on both macOS and Windows

—Any video-playback

—live streaming and video-conferencing

— gaming

—useless aftermarket anti-virus and so-called "cleaning" apps.

— external monitors

Even some web pages opened with a lower-impact browser like Brave or Safari can increase workload. I'm seeing that of a lot of retail sties' pages with a "buy now" or "add to cart" button will show up high work load in Activity Monitor.

Some diagnostics may help us. Please find System Information

in Launchpad and open it. Select "Power" from the left-hand contents pane and tell us what eh reslut main pane screen shows for "Health Information" here:

That can help us determine if your battery is ailing or simply used "up."

QuantumVerse111 wrote:

You bought your MacBook three years ago

Now, it feels like you can’t step away from a charger for long. What happened?

Lithium laptop batteries usually to need replaced between 3-5 years. Some may need replaced sooner & some people may not notice a problem until much later.

A lot of factors affect the health of a battery....age of the battery is one of those factors.

If the Battery Condition is "Service Recommended" or if it fails the Apple Diagnostics, then Apple or an Apple Authorized Service Provider can replace the battery for you. Otherwise it may be tricky to have Apple replace the battery since Apple will usually only replace the battery if it is showing those conditions.