In October 2005 the California Building Energy Efficiency Standards adopted new standards for energy efficiency. The new standards will increase overall energy efficiency requirements and introduce a new metric for measuring the impact of on-peak energy use. The methodology is called Time Dependent Valuation (TDV).

Time Dependent Valuation (TDV)
For many years, the standards have used a constant multiplier of source energy (kBtu/ft2) consumption as the metric for determining compliance. For the 2005 standards, the source energy multiplier is replaced with a dynamic multiplier correlating each hour of the year by climate zone and more accurately reflecting the cost of generating and delivering electricity at each hour by California’s electric utilities. The new standards establish a maximum kBtu/ft2 as derived from multiplying each of the proposed building’s 8,760 hours of energy use by the associated climate zone dependent multiplier. Compliance with the standard is obtained though simulation modeling and measurement against the standard’s maximum allowable annual TDV energy use for the building type and location.

A graphic illustration of the nonresidential standard’s range of TDV multipliers clearly shows the greatest multipliers occur at peak air-conditioning use hours of the year. The TDV multiplier range varies from a value of 10 during spring nights to over 80 on August afternoons. The graph for residential TDV multipliers shows similar ranges.