Generally both Chrome and Firefox are significantly worse for battery life under macOS than Safari is. I think the main thing is that standalone browser vendor

Generally both Chrome and Firefox are significantly worse for battery life under macOS than Safari is. I think the main thing is that standalone browser vendors aren’t incentivized to care all that much about being efficient; for them acing speed benchmarks and gee-whiz bells and whistles seems to be what sells better. By contrast OS vendors want battery life figures to look great because that sells laptops. This is why pre-Chromium MS Edge bested Chrome and Firefox for battery life on Windows and why Safari does the same on macOS today.