Upgrade your HVAC system.

“Upgrading to a “U.S. South” ENERGY STAR certification can save you up to 12% on your heating bill, or an average of $36 per year. ENERGY STAR furnaces in the northern half of the U.S. are labeled with the standard ENERGY STAR logo and are up to 16% more energy efficient than baseline models. This translates to average savings of $94 per year on your heating bill in the Northern U.S. ‘

https://www.energysage.com/energy-efficiency/101/ways-to-save-energy/