Rising sensitivity of the society for environmental aspects led to legislation limiting the CO2 emissions of vehicles and customer relevant demand for high fuel efficiency. This necessitates high-efficiency engines with lower heat rejection rates, which has progressively reduced the amount of available 'waste' heat for compartment heating. In an effort to reduce compartment heat up time while increasing the compartment temperature, a new PTC (positive temperature coefficient) electric heater system has been developed to supplement the performance of current engine coolant based vehicle heaters. The PTC supplemental heater system features automatic power adjustment in response to cabin heating requirement, ambient temperature conditions, engine coolant heat up rate, auxiliary.s power requirement along with self regulation of the heater temperature. In addition, the low cost Electronic Control Unit (ECU) takes a stock of on-board available power from the alternator taking into account status of other electrical loads. Based on these inputs it implements a rule base for optimising driver comfort by switching ON appropriate number of heaters for all vehicle operating conditions. A system model based on alternator characteristics and cabin temperature mapping based on coolant temperature is stored in the ECU memory. The ECU also provides K-line connectivity for calibration/tuning and diagnostics. This paper describes the construction, performance mapping and validation approach adapted for development of PTC supplemental heater system. Supplemental PTC heater with controller was developed as per the set logic which uses environmental parameters (used to give permission to turn the PTC heater ON) and power net management parameters (used to adapt the power consumption of PTC heater to available electrical power). Although the goal is to reach 100 % of PTC heater capacity the alternator cannot always give the PTC heater all power that it needs. The PTC driver must then adapt the heating power to the electrical power available. Tests conducted with developed PTC heater system showed average vehicle compartment temperature improvement of 5 to 6 deg C under steady state driving conditions. The improvement under transient driving conditions were limited to 3 to 3.5 deg C due to constraint of available electrical power. Electrical charge balance with PTC heater ON in a city drive condition observed is + 3.5 % under transient driving conditions.