There's some potential for the new WebRender stack to improve battery life a lot - part of the reason why Edge is so good at saving battery is that it makes good use of modern GPUs to save power, and Firefox's new graphics stack is another modern one that attempts to avoid wasting CPU/GPU to do old-style rendering of web pages

It's really that we should be using the OS compositor more than we are, particularly on macOS. I think I'm probably going to be working on this, or at least finding someone to work on it, soon. WebRender should make this easier, because we should be able to get away with using a smaller subset of the OS composition functionality than other browsers do.

Anyway, for now, if you're on macOS, set gfx.compositor.glcontext.opaque to true in about:config for a large increase in energy efficiency at the cost of some visual effects.

One would think that would be as a direct result of consuming more resources, not less. What is it doing to drain your power, do you know?

I really want to switch from Chrome -> Firefox for dev work but my MBP’s battery already lasts nowhere near “10 hours”...

Last time I played around with comparing, Chrome and Firefox were comparable in terms of battery drain on my MBP. However they were both significantly worse than Safari, which barely ever turns on the discrete GPU while I'm browsing.

Well, if you're looking for battery life, both safari and edge have excellent battery life by virtue of not doing anything useful.

And if you're looking to do dev work, that usually means at minimum an editor, a server, and a browser, which seems like too much to run unplugged.

Unless your editor is actually a webapp itself, I don't see how that's going to tip anything over the edge in terms of practicality...

The resources consumed by any web server I can think of are entirely inconsequential.

Or fortunately for those of us who use desktop computers. Usually battery performance enhancements decrease actual performance. It's a real shame so much good software is gimped just so people can run it on mobile.

This hasn't been true for a long time. The same enhancements that conserve battery also tend to ensure that plenty of processing and thermal capacity is available for whatever does want the CPU. (For instance, your top CPU "turbo" speed depends on how many of the other CPU cores are sleeping.)