ZNET: Zero Net Energy Including Transportation

July 29, 2015
Session W3C: Community Solar and Net Zero Strategies for the New Energy Economy — Room 106
1:30 pm  -  2:30 pm

“California has a “Big Bold Energy Efficiency Strategy” that all new residential construction will be net zero energy (NZE) by 2020. Two things noticeably absent from California’s strategy were: (1) the exclusion of existing residential buildings; and (2) the exclusion of personal transportation. Hoff and Ressler defined the ZNET concept in a 2014 ASES paper in response to this strategy. The authors analytically demonstrated that California could pursue a strategy wherein all residential buildings (existing and new) are NZE while broadening the definition of NZE to include personal transportation. The concept was described as ZNET: Zero Net Energy including Transportation.

The findings of that paper led to the decision to demonstrate the ZNET concept in an existing house. The selected house was a typical 30-year old, 3,000 square foot tract house that consumed approximately 50,000 kWh per year of site energy, including electricity, natural gas, and gasoline. Two key decisions were made for the demonstration. First, the project had to have a payback of less than ten years. Second, the project needed to be implemented without any major retrofit (i.e., no deep energy retrofit or gutting of the house). These goals were accomplished using vampire load reduction, LED lights, switch one car from gas-powered to electric vehicle, improved building sealing, insulation and ventilation, heat pump water heater, HVAC system change, and installation of a 6 kW-DC PV system.

The project has been deemed a success after about one year of testing. There was a 90 percent reduction in net site energy consumption, including electricity, natural gas, and gasoline. The project had a simple payback of approximately 6 years. Addition of a second electric vehicle would reduce net consumption to 0 kWh.

The paper will present one year of measured results for the project and describe potential implications.”