Older furnaces usually have a PSC motor and could cost a little over $1 a day electrically to operate the furnace fan. When it comes on it comes on in full force whether it’s needed or not. . Furnaces manufactured after July 2019 are equipped with energy efficient motors. These motors can adjust the air flow based on the temperature needs and could operate per pennies per day. If you have an older furnace, the motor can be upgraded to an ECM motor. Some Electric Utility companies even offer a rebate for the upgrade replacement.