Call Chancey & Reynolds if you're in Knoxville area.
Especially if you need a new unit. I did the TVA Energyrite program about 18 months ago. I live in West Knox County. After checking out all of the major HVAC companies from Strawberry Plains to Lenoir City to Oak Ridge to Maryville and all points inbetween. Even outliers like Kingston and Sweetwater.
I needed a total new system, including ductwork, up and down. They are large enough they have their own design office & warehouse with breakmetal and cutting machines to make industrial grade plenum installations. Yet, they have over a dozen trucks running around doing residential service and installations. Even a dedicated supervisor traveling site to site as needed to troubleshoot or bring needed parts. Truly the best HVAC co. around, and my installation was at least 15% cheaper than any of the other eight comparable outdoor compressor/indoor airhandler/filter/total ductwork/programmable thermostat quotes. Settled on them and have no regrets.