From Carl's Guide:
Going Green
So, if you want to make your Sims Neighborhood have a Green Eco-Footprint you need to build with green materials, and place objects like the new solar panels, wind turbines, and dew collectors. Other means of power and water generation are more toward the industrial side. Like using regular fuel instead of bio-fuel. If you struggle to move the needle, go into build mode and make modifications to the neighbors' homes to improve the neighborhood's average in order to make it green. You could just add a bunch of windows with green values, and change all wall coverings to be green. The fact that this costs you nothing is frustrating to me, because it means my Sim's actions matter less.
https://www.carls-sims-4-guide.com/expansionpacks/ecolifestyle/eco-footprint.php
