First decide the energy bill is something that should be addressed.
Working up a plan from the most cost-efficient to more involved “bragging rights” solutions first start with a $75 Home Energy Solutions audit:
http://www.clp.com/home/saveenergy/rebates/homeenergysolutions.aspx.
Then consider an alternative that’s not quite yet on the market: sheetrock that radiates stored energy! http://www.fastcompany.com/1539050/coming-soon-melting-drywall-cools-your-home