An integrated mechanical, electrical and plumbing appliance includes a housing defining a space occupied by an air treatment system, an electric power system, and a water treatment system. The electric power system includes a divides electrical power from an electrical power source connection into electrical circuit feeds for delivery within the housing to the air treatment system and the water treatment system, and to a building. The air treatment system includes receives exhaust air from the building and uses the exhaust air to precondition outdoor air, and receives return air from the building and conditions the return air. The water treatment system receives water from outside the building and divides the water into a water flow for output to the building and water flow to be filtered, filters water and outputs unheated water to the building, and heats water for output to the building.