Well, I’ve traded burning fuel for burning internet and electricity at my home. My electricity at home is mostly solar (from my roof) and hydro from the grid (I live in Washington State).
Working from home spares me ~20 uncompensated transit hours a week, so the emissions difference (whether I use transit or drive) is substantial and so is the cost savings (in fuel and parking). FWIW, my employer will pay for my transit fares (but not fuel or parking) and that’s nice and all, but I’m squeamish about transit during flu/covid season because of all those coughing people going in to jobs that don’t encourage them to stay home while sick.
I’m able to work more hours when I do it from home because I’m not constrained by transit schedules/catching the last train out of town, and that way I still come out ahead in terms of having time with my kids, and I have time to take grocery shopping and meal planning and prep off of my wife’s plate.
It’s better this way, not just in terms of cost and environmental impact and quality of life, but productivity-wise.