In the present research thermal performance of earth air tunnel heat exchanger (EATHE) coupled with a solar air heating duct has been experimentally evaluated for arid climate of Ajmer city of northwestern India, during winter season. An attempt has been made to enhance the heating capacity of EATHE system by coupling it with a solar air heating duct at the exit end. Results show that the air which comes out of coupled EATHE system is relatively hotter than the air supplied by the stand alone EATHE system. It was found that the heating capacity of EATHE system got increased by 1217.625-1280.753 kWh when it was coupled with solar air heating duct with a substantial increase in room temperature by 1.1-3.5 degrees C. The COP of the system also increased up to 4.57 when assisted with solar air heating duct. Therefore, the heating capacity of EATHE can be significantly increased by coupling it with solar air heating duct. (C) 2014 Elsevier B.V. All rights reserved.