Case study of a DOE Zero Energy Ready home in Houston, TX, that achieves a HERS 45 without PV or HERS 32 with 1.2 kW PV. The three-story, 4,507-ft2 custom home is powered by a unique tri-generation system that supplies all of the home’s electricity, heating, and cooling on site. The tri-generator is powered by a small efficient natural gas generator that produces electricity with photovoltaic and battery backup. The generator’s belt also mechanically drives the compressor for the home’s air conditioner. Coolant carries heat from the generator engine to heat domestic hot water, a fan coil in the air handler for space heating, the clothes dryer, and the desiccant dryer for the home’s dehumidification system.