The experimental studies were conducted to study the plastic thermoforming heating process. The heaters performance has been evaluated from two different ways: heating water calorimeter for heating efficiency and heating plastics for thermoform processes. The studies of the heaters include gas-fired heater and electric heater. Transient heating processes of plastics were also studied to investigate the heater’s performance on plastics. The surface temperature of plastic at the end of heating process was measured by IR camera. The heating cycle time, surface temperature uniformity of plastic and energy consumed for the heating cycle by different heaters were discussed. The pros and cons of different heaters for plastic heating process were also discussed in this paper.