In this paper, the authors develop enhanced energy consumption model to calculate and compare the hardware energy consumption of SPI and I2C digital serial interfaces in PIC (Programmable Interface Controllers) microcontrollers and analyze using software simulation tools. Energy consumption of two digital serial interfaces (SPI and I2C) in PIC 16F877 has been measured and compared. Serial communication between two microcontroller(one master-one slave) is performed using SPI and I2C protocols, one-byte data has been transmitted from Master to Slave and displayed in two 7-segment LED’s and using a digital oscilloscope, wave forms in SPI and I2C interface lines(to send clock signal, one-byte data and the chip select) were observed.