Cleantech Market Intelligence
California Calculates the Value of Time in Energy Efficiency
The 2013 update to California’s Title 24 building energy efficiency standards went into effect on July 1, 2014. In addition to increasing overall building efficiency requirements over the 2008 standards, this update sets out more stringent lighting requirements for both residential and non-residential buildings.
The 2013 update also includes changes to California’s time dependent valuation (TDV) calculation. Used only in California, TDV is a tool to gauge the value of energy efficiency measures. Unlike other metrics, such as site or source energy (measured in kBtu), TDV includes the cost to provide energy based on time of use, as well as other variations in cost due to climate, geography, and fuel type.
TDV was developed in 2005 and was updated in both 2008 and 2013 to help California meet the energy efficiency goals established in Title 24. In the 2013 update, the California Energy Commission (CEC) changed the TDV calculation to account for climate sensitivity by separating California into 16 different climate zones. This alteration helps reflect differences in energy costs driven by climate conditions, which vary considerably throughout California.
One of the key barriers to wider TDV adoption is developing values for each climate zone. As stated above, California alone has 16 climate zone values. Another limitation is that many state officials are unaware of it. California is the only state that uses TDV, whereas metrics such as site and source energy are much more commonly employed both nationally and internationally. Furthermore, TDV does not account for the potential grid modernization costs necessary to export excess electricity back to the grid.
But since TDV accounts for differing energy costs based on a range of factors, it more accurately captures the societal cost of energy consumption that’s missed in assessments based only on source or site energy parameters.
In the coming years, as California tries to build more zero energy buildings (ZEBs), TDV will play an important role in determining whether a building meets the required energy use intensity to qualify as zero net energy. The forthcoming Navigant Research report, Zero Energy Buildings, will provide an update to the 2012 iteration and look further into the benefits and challenges associated with TDV as a metric.