A modular solar air heater comprises an extruded metal frame having fingers operable to secure a glazing, an absorber, and an insulating back sheet to the frame. The heater may also operate as a cooler. The heater further comprises an active air circulation system, such as a fan, which may be coupled with an air inlet of the heater. The heater has an air outlet and may further include a bypass channel to direct the airflow alternatively through one or both the bypass channel and the air outlet. A heating element and a cooling element may be coupled with the air outlet to further heat and also cool the air through the air outlet, respectively. A photovoltaic panel may be included to provide electrical power to the heater.