Inverter/ Uninterrupted Power Supply System eliminates issues like insufficient thermal backup for indoor telecom BTS sheltering, switching of existing systems to dg due to temperature increase. The System has the feature that when there is a rise in shelter temperature, thermal backup happens with the battery and avoids the utilization of DG. The System ensures good space utilization because of the compact design and no surge effect on battery due to the soft start. The System extends the thermal backup and ensures that battery bank is thoroughly utilized and initial surge load on battery bank is avoided because of their soft start capabilities. The Inverter/ Uninterrupted Power Supply System can be used in the telecom networks for ac loads by utilizing the services of the existing battery and ensures low power loss and a high efficiency of around 93%.