Abstract: A solar hot air system is provided containing a solar hot air collector and an inlet duct connected to the solar hot air collector and a building fresh air intake. A sensor is connected to the building fresh air intake, configured to measure fan speed and damper position. In addition, a sensor is connected to the inlet duct, configured to measure air volume and temperature. Further, a sensor is connected to the solar hot air collector, configured to measure internal and ambient temperature. A means for calculating a periodic fee to a user based at least in part upon an amount of generated energy is also provided.