Industry 4.0 aims at highly flexible and digitized model of industrial production that is smarter and more reliable than the current possibilities. This requires vertical integration of different operations in a manufacturing to promote reconfigurable smart factory. This investigation proposes a method to schedule maintenance operations using formal methods considering power balance and production constraints in process industries. First, we provide an optimization model for scheduling maintenance and operation along production schedules. Second, we use timed model checking to schedule maintenance considering various physical and operating constraints. Third, we illustrate the method in a smart aluminium factory. The main contribution of this investigation is the integration of optimization models and formal methods in one framework, which leads to verified production/maintenance schedules and contributes to the objectives of Industry 4.0.