In this book an efficient solar power controller (SPC), suitable for constant load applications under different solar radiation is proposed. The proposed SPC is able to overcome insufficient solar radiation problem and can maintain constant power at the load end. The proposed controller provides constant power at constant terminal voltage (125V) and charges the battery when photo-voltaic (PV) generated power is greater than load requirements. During cloudy weather or when panel output power is insufficient to maintain constant power at load end, the controller takes required power from the battery. This controller has almost constant efficiency about 87% at full load.