Zero Net Energy Production Builder Demonstration

Pacific Gas and Electric Company (PG&E) implemented a Zero Net Energy (ZNE) Production Builder Demonstration that supported six builders in California in designing and monitoring a ZNE house. Each builder received technical support from start to finish to upgrade one of their existing prototypes to ZNE while preserving their look and feel. The ultimate goal was to achieve a ZNE home that the builder could replicate to begin to build ZNE homes at scale. For each builder, the design consultants recommended energy efficiency measures for the builder’s standard design based on performance modeling and substantial past experience with ZNE and energy-efficient homes. As part of this offering, PG&E reimbursed up to $15,000 in incremental cost of the energy efficiency measures; experience shows that the incremental costs will drop in subsequent projects. Finally, the monitoring consultants tracked the end-use energy consumption of the completed home for a year after occupancy to determine whether the ZNE home is performing as designed and to diagnose any operational issues.

Although the participating projects are in both marine and hot dry climates and built for low income and market rate occupants, there were several common design features. At least four used 2x6, 24” on center wood framing, located their ducts in semi-conditioned or conditioned space, provided heat pumps for space conditioning, installed condensing gas water heaters, and installed 100% LED lighting. The modeled energy use intensities (EUIs) of the ZNE designs vary from 15 to 27 kBtu/sf/yr, representing a reduction of 3-55% below the builder’s standard practice.

The measured energy consumption data was compared to energy models using typical and actual weather for the location. The measured consumption was greater than predicted in all cases based on actual weather condition and in five of six cases using typical weather. The measured energy consumption data shows that California energy code has effectively reduced HVAC energy through tightening building envelope requirements so that hot water was the biggest end use in most cases. The combination of appliances and plug loads, which are not be regulated by California building energy codes, accounted for 30-47% of measured consumption. One of the most effective efficiency measures that is available to builders is supplying highly efficient appliances since occupants may otherwise choose inefficient models.

The ZNE homes built as a part of this effort provide a base for each builder to iterate on as they refine their strategies and processes and increase the efficiency of their homes.

The body of this report describes the overall demonstration, the design and monitored performance of the houses, and some lessons learned. The appendices contain detailed design and monitoring case studies of five of the builder projects.

In addition detailed reports about the individual buildings are available:

Brentwood:  link 

Clovis:  link 

Greenfield (CHISPA):  link

Hayward:  link

Loomis:  link 

Stockton: link