IEEE Accurate and fast estimation of single phase grid voltage phase and frequency has the potential to improve the performances of various control and monitoring techniques used in electric power system. This letter applies an adaptive sliding mode observer for frequency and phase estimation. The observer is simple, easy to tune and suitable for real-time implementation. The proposed adaptive observer can be considered as an alternative to phase-locked loop (PLL) with better performance. dSPACE based experimental results are given to show the effectiveness and performance improvement of the proposed approach with respect to two other advanced PLL techniques namely pseudo linear - enhanced PLL (PL-EPLL) and Second order generalized integrator- frequency locked loop (SOGI-FLL).