Some time ago I started paying attention to power consumption of all the stuff I'm buying. I replaced last old light bulbs with low-energy ones and led lamps. When I bought new home theatre and TV few years ago, I chose ones that have very low stand-by power. In my TV it is 0,2 watts, compared to my old TV that used nearly 7 watts! What the hell it was doing with that? New TV is still showing little red light and start from the remote, just like the old one. My computer have SSD drives and low power HD for storage. Monitor uses about 22 watts, compared to old that used over 60 even though it was much smaller.
And this have worked indeed. My apartment total power consumption have dropped from 1366 kWh to 808 kWh during last 5 years.
And this is without any other efforts. Stuff like turning off the lights every time I leave the room and things like that. Instead I'm sure I've been using all kind of electric gizmos even more during last years, bought Roomba etc.
I recommend this to other people, additional "work" that is needed when buying stuff is minimal. Surely saves money in long run, but environment too :)