Ran through everything with Apple and they said it is a Firefox issues.

Okay..

Did you test that theory by not using Firefox for 12 hours and only using Safari to see if you can get the purported 12 hours?

I did not. I will try. Thank you

Also, I know it is Firefox because of energy level indicated on activity monitor. My preference would be to find. a fix to continue to use Firefox instead of Safari or Chrome. But will check with Safari.

This will be interesting, but Firefox does have this going on in the background.

Firefox's Project Fission:

Introducing Firefox’s new Site Isolation Security Architecture https://hacks.mozilla.org/2021/05/introducing-firefox-new-site-isolation-security-architecture/

Firefox's Project Fission: better security and more processes https://www.ghacks.net/2019/02/07/firefoxs-project-fission-better-security-and-more-processes/

You can try Firefox's Site Isolation feature Fission in Nightly now https://www.ghacks.net/2020/09/20/you-can-try-firefoxs-site-isolation-feature-fission-in-nightly-now/

Change how many processes multi-process Firefox uses https://www.ghacks.net/2016/02/15/change-how-many-processes-multi-process-firefox-uses/

Thank you very much.... weird that with all the Firefox users no one else is really reporting this and these articles are so many years old. Nothing recently as a common problem.

Oh no... there are many users complaining about resource usage, but they tend to have very little resources from the start. Still waiting on that experiment comparing using Safari and no Firefox for several hours.

So, I compared the Safari to Firefox (sorry took so long). Same. I got about 3 hours.

No problem, we applaud the effort. It's all advertising when they talk about batter life. Will there be anything else?  ;-))

No, not unless you know how to get more than 3 hours on a new computer. Thank you!

Mark it as resolved and we'll leave the light on for ya.  ;-))