TLS takes considerably more watts of power on the basis it actually does more work and shuffles more electrons around the CPU. I suppose that loosely converts into carbon footprint.

However even if it is an issue, most sites sending 6 meg of JavaScript crap down that gets recompiled on every visitor’s machine, autoplaying videos and advertising would be doing more damage. So if anyone is going to complain they should probably start there...

A proxy can't cache the ressources anymore. SSL overhead, CPU used by both parties to do the encryption. But the ISP can't alter the page.