https://www.cnet.com/news/smart-home-tech-that-can-save-you-money/

Better yet, they make it easier to efficiently maintain your home at a comfortable temperature. Nest's thermostat learns and adapts to your preferences over time. Ecobee's comes with a remote sensor so you can adjust the temperature based on a specific room. 

LED bulbs are exponentially more efficient than old-school incandescents, whether they're smart or not. If you want to save big on your electric bill, LED bulbs are a great place to start. And as they become more common, prices for individual bulbs are going down. A couple of years ago, good smart bulbs could cost $60 or more each. Now you can readily find packs of two for $25.