Abstract: An automated control system for a dual-fuel boiler, engine, or other apparatus continuously monitors the consumption of a primary fuel source and automatically switches from the primary fuel source to a secondary fuel source when a predetermined amount of the primary fuel is used in a measured time period, the object of the system being to automatically maintain a 100% load factor of the primary fuel source. A meter continuously monitors consumption of the primary fuel and outputs an electronic flow signal representing consumption of primary fuel. The flow signal is received by a programmable logic controller having a real-time clock whereby consumption of the primary fuel is measured against time. Remote control actuated ball valves mounted in the primary and secondary fuel lines selectively control the flow of primary and secondary fuels to the dual-fuel apparatus.