Simulation of tree shade impacts on residential energy use for space conditioning in Sacramento

The Sacramento Municipal Utility District (SMUD) and the Sacramento Tree Foundation (STF) have collaborated for many years to plant shade trees with the goal of reducing energy use. This paper, published early in that collaboration, modeled the benefits of the program. A sample of properties were chosen randomly. Data on trees and buildings were taken from the Tree Care Agreements written up by STF staff, and shade effects were modeled with the Shadow Pattern Simulator. These data were combined with weather data in the Micropas program to determine the energy benefits of the sampled trees. Substantial cooling effects were found that extended through approximately the sixth tree on a given property. Negative effects on winter heating costs of about 1/3 of cooling savings were found, with a net energy savings of about $14 per tree.