The aim of this paper is to develop a wireless sensor network to measure and analyze energy consumption in buildings and to investigate the bounds of coverage in different building construction materials. The performance of the designed system is evaluated in different indoor channel conditions using both computer simulations and hardware measurements. The basic design elements include current sensors, microcontrollers, and wireless transceivers implemented using GSM/GPRS platform and ZigBee technology. The use of GSM/GPRS platform makes it possible to control or gather information about the system from anywhere just by sending a request using SMS. Many measurements have been done to find the exact limitation of the designed system in terms of coverage and signal strength in the presence of objects of different materials including: cardboard, metal, concrete bricks, wood and corkboard. The results show that the metal represents the worst material in terms of signal strength reduction. At 4m distance between the base station and the sensing node, the loss in signal strength are 15, 20, 21 and 32 dBm when using metal as compared with cardboard, corkboard, wood and concrete bricks respectively.