An apparatus and method for portable calibration of electrofusion controllers. The method includes providing a portable self-contained calibration device to an electrofusion controller. The calibration device includes internal or external dummy loads to simulate real fittings to be fused and instructs the electrofusion controller to apply electricity to these dummy load. Then, the calibration device uses a measurement sub-system to measure a pre-determined parameter. A microcontroller sub-system determines if there is a difference between the measured values and the expected values. If there is a difference, the calibration device adjusts the electrofusion controller's memory. The calibration device repeats the measurement with a second independent measurement device to ensure accuracy.