We can often easily substitute planes for trains for absolutely massive gains. I don't think there are massive gains to be had for tech. I'm sure someone will show me a post about how C uses a few watts less but its not even close to the gains that can be had elsewhere.
From what I see in companies, probably half of the data and workloads out there are pretty much useless or barely used. At home, I think most of us could do a better job by shutting down everything when we are away.
