Abstract: The invention provides a low electric power-consuming heating or cooling system comprising a DC powered microprocessor-based control system and method and a DC powered electrically actuated zone valve. The control system operates on DC power allowing the heating or cooling system to operate independently of electrical utility grid power, without compromising heating system safety. Electric power consumption is minimized by using very energy efficient DC powered devices and circuit components, and a very energy efficient DC powered zone valve. The control system detects and displays errors in the system and transmits audio-visual alarms when errors are detected, and is also capable of communicating with external computers for data storage and error diagnosis. The zone valve actuator uses DC power and DC electrical and electronic components. The position of the valve is indicated by a sensing system, and valve position is known a priori without rotating the valve.