The Reliable Renewable Geothermal gives you the freedom to focus on life WaterFurnace geothermal systems provide reliable operation 24 hours a day, 7 days a week, 365 days a year—rain or shine, day or night, windy or not. They use the stored solar energy in the ground to provide your family luxurious comfort and incredible savings. Now with a renewed 30% federal tax credit*, there’s never been a better time to switch to the Reliable Renewable. Want to know how much you can expect to save on your energy costs with a geothermal system in Knox County, Cosby Heating and Cooling? Find out with our geothermal savings calculator! * The 30% credit is available through the end of 2019, but it’s set to decrease each year through 2021. The credit amount drops to 26% in 2020 and down to 22% in 2021.