Design of this heater is a part of measurement device that will be applied to measuring heat transfer of evaporation coefficient value. Electric heater serves to variation a quality of refrigerant vapor which is one of the variables to determine the value of evaporation heat transfer coefficient with refrigerant R-134a as working fluid and the position measurement device is horizontal and vertical position. The design of the heater done by 2 methods that is experimentally and Semi theoretical method. On the experimental method initial data done to determine m each inverter variation is 14,16,18,20 and 22 Hz and the value of h3 = h4, hf, and hg, to calculate Qrefrigerant for quality (saturated liquid becomes saturated vapor) . To determine Qheater is done by calibration of water with assumption (QRefrigeran = Q absorbed water). To make a experimental heater includes the process of selecting heating wire, heating wire heating test, determining the length of the heating wire, and the selection of insulating material. Based on the semitheoretical method, Qrefrigerant is determined by knowing the entalpy value for each vapor quality. The heater power is determined based on the calculation that Qheater = QRefrigeran + Qloss. The Qloss value is determined by assuming the outer surface temperature of the insulation. The critical radius of the insulating material is determined by the variation of the free h convection value obtained from the calculation of the Qloss value. The insulating material specified to determined critical radius is glasswool. The design result based on experimental method of maximum heater power 3205,68 Watt (x 0-1). Heating wire used Nicrome Ni 80 AWG 24. Heating wire length 2.5 m wound 3 for 1 voltage regulator. Insulating materials are gypsum rings, asbestos tape, glasswool, and aluminum foil. The performance results indicated that the heater was made capable of altering the vapor quality even though not exactly with the deviation of 18.51% and 26.86%. Based on the semi theoretical method of maximum heater power 1651,22 Watt with Qloss 35,19 Watt. With 5.2 m heating wire length. From the graph between ri-r and Rt value indicates the thicker the glasswool insulation the better. Recommended thickness is minimum 15 mm.