Based on the data provided in The 2015 City Energy Efficiency Scorecard , The rank of energy saving in US 2015 is list below:
1.Boston MA 2.New York City NY 3.Washington DC 4.San Francisco CA 5.Seattle WA
Here's a graph created based on the data
Graph created by myself
The GREYSTAR company claim they have very much concern about the environment "Greystar believes that energy management and sustainable practices enhance the financial value of the communities we manage and help to preserve the environment for future generations"
They provide few samples of their apartment energy-saving projects
Also a video shows their contribution to environment protection