Tech uses power and produces heat, so anything helps if it reduces the amount of tech being run and kept 24/7 in climate-controlled spaces. That goes for severs, but also for big hot monitors in your office (hold your hands over an apple cinema display some time - you'll realise why your office heats up). Measuring that is harder, particularly when "dust cost" comes in (total environmental cost of something including manufacture, shipping, maintenance, power, decommission and disposal). It's probably only going to make a major dint if your product is consumed at scale.
Partly I think we can help by being a little frugal in our tech purchases and what we push on our customers. Buy new workstations every three years, rather than two; buy laptops and set frugal power settings (why shouldn't it go to sleep after 5 inactive minutes?). Don't upgrade your phone every year.
But more than that - don't build products that only work on this year's gadgets. I have an original Nexus 7 that I still use daily, but it's struggling eg. I use Facebook via https://mbasic.facebook.com (which is awesome and I applaud Facebook for providing it) since the app and main website crash. Kindle app is slow and often needs a restart. Google's own apps are slow and there are too many pushed to the device that I don't need.
The point to consider is I don't do anything now that needs more power than it did four years ago. In fact I use the device for precisely the same things that worked beautifully on its release. It's in great condition and should still work, it's only the software that has changed - and people feel that's fine since this device is "so old".
Four years should not be an extraordinary lifespan for a small consumer device. The OS and apps should not have become so hungry so fast. Before anyone tries to say Apple devices are different, I also have a gen1 iPad which went the same way in less time and although I was lucky enough to win it; had I paid it would have cost around 4x as much as the Nexus 7.
We should build things that work on old, slower devices; because that leads to less nasty e-waste which is expensive to recycle - if it gets recycled at all and not dumped in landfill.