## Time Dependent Valuation

The California Title 24 Building Energy Efficiency Standards have utilized a Time Dependent Valuation (TDV) methodology since 2005 to account for the time value of energy for load and for self-generation credit. TDV is a composite measure of the actual cost of energy (for each of electricity, natural gas, and propane) to the utility, customers, and society at large. It has been crafted for evaluating energy efficiency savings based on when those savings manifest. The TDV sources and methods have recently been updated for 2019 (Ming, et al., 2017).

The TDV concept allows even-footing comparison of a set of time-series simulations of how different building designs use energy. Accordingly, it is the mechanism by which the CBECC-Res 2019 compliance software converts a residential battery’s load shaping patterns into a self-utilization credit. If a building charges a battery from on-site PV during midday, the simulation foregoes a small TDV credit for power it would have fed to the grid. When the battery discharges in the evening, it can earn a much larger credit for reducing load when TDV is high. That net-TDV reduction counts toward reducing the building’s design EDR.