An indoor environmental condition control and energy management system includes a plurality of inputs. A user input receives user input parameters including a desired indoor environmental condition range for at least one energy unit price point. An indoor environmental condition input receives a sensed indoor environmental condition. An energy price input receives a schedule of projected energy unit prices per time periods. A processor, coupled to the inputs, computes an environmental condition deadband range for multiple energy unit price points based on the user input parameters and controls at least one energy-consuming load device to maintain the indoor environmental condition within the computed deadband range for a then-current energy unit price point. In an embodiment, the environmental condition includes at least temperature and the at least one load device includes a heating and cooling system. The processor, in one embodiment, communicates through a communications link with at least one energy supply company and selects one energy supply company for a premise to minimize energy consumption cost.