Ragin' Air is a professional HVAC company that specializes in heating and cooling systems. When it comes to furnaces, there are several factors to consider in order to find the most energy-efficient option. Generally, high-efficiency furnaces with an Annual Fuel Utilization Efficiency (AFUE) rating of 90% or higher are considered the most energy-efficient. These furnaces utilize advanced technology to extract and utilize more heat from fuel sources, resulting in higher energy savings.