Shade Trees: Tree Benefits Estimator
The Tree Benefit Estimator Was Designed to Help You
This Web-based application will help APPA member utilities quantify and track the benefits of planting shade trees. It estimates the amount of energy savings (KWh saved), capacity savings (KW saved) and carbon and CO2 sequestration (lbs) resulting from mature trees planted in urban and suburban settings. The Tree Benefits Estimator can be used by those who have no formal background in urban forestry or Demand Side Management (DSM) utility practices.
Tracking the Benefits of Tree-Planting Efforts is Necessary
One of the greatest challenges facing public power today is environmental stewardship. It is increasingly important that public power utilities not only take steps toward local environmental improvements, but measure the effectiveness of their efforts. The measurements are important to local communities in understanding how they can control their environmental future and the cost of doing so. It is also important for utilities to be able to measure environmental impacts that in the future may be reported to state and federal governments on a voluntary or mandatory basis.
What You Need to Know About the Estimator
The Tree Benefit Estimator, developed by Sacramento Municipal Utility District (SMUD), was based on the experience of the SMUD's Shade Tree program. In developing this simplified and easy-to-use method for estimating the tree planting benefits, broad assumptions have been made regarding trees' impact on direct shading benefits, impacts of indirect or evapotranspiration effect, heating penalty in winter months, tree growth rates and tree survival rates. As a result, this method may yield less precise results than a more tailored approach. Staff from the Center for Urban Forest Research, Pacific Southwest Research Station, USDA Forest Service, University of California, Davis, have reviewed the Tree Benefits Estimator.
What You Need to Know About Your Trees
1. the average cost of electricity in summer and winter months (cost of KWh)
2. the tree species (common OR botanical name);
3. the age of the tree from the tree planting date OR the tree diameter at the breast height (DBH).
4. the number of trees planted (1 or more)
5. the location in the US, which would determine the climate zone
6. the direction your tree faces (for trees planted next to buildings);
7. the distance between the tree and the building that is being shaded;
Items to Consider
To take into account different climate zones, you will need to input information about the standardized climate zones or regions in the US and then the Tree Benefit Estimator© would calculate the impact of ambient temperature and relative humidity on the summer cooling load and winter heating requirements using the Cooling and Heating Degree Days and Latent Enthalpy Hours data. The summer cooling load requirements and winter heating penalty are essentially a function of the cooling and heating degree days and direct shading impacts. The KWh impact of the tree evapotranspiration effect (or indirect effects) is essentially a function of the Latent Enthalpy Hours. However, regardless of whether a tree is planted for the energy saving benefits, the method will estimate carbon and CO2 sequestration values for the specified tree species.
The methodology is based on the "standard" nursery raised trees which are typically sold in 5-gallon containers, and which are usually 1 inch in diameter at the tree base (1 foot above the ground). (SMUD Shade Tree program has experienced that 5-gallon container trees will grow quickly and catch up with the larger 15-gallon container trees within the next couple of years and thus the methodology applies for both 5- and 15-gallon container trees.) This methodology assumes that the standard (5 gallon) trees are "0" age when planted. The Tree Benefit Estimator© will provide the estimates for the large selection of common species of deciduous, broad leaf evergreen and conifer trees in the US.
For the existing trees, the age of the tree from the planting date OR the tree diameter at the breast height (DBH) information the will then determine the tree growth rate factor, which will in turn determine the level of energy and carbon sequestration benefits for any year.
For the Program Trees or the trees planted by the utility, the age of the tree from the planting date OR the tree diameter at the breast height AND the tree survival rate factor in that year will then determine together the Program Tree factor, which will then determine the level of energy and carbon sequestration benefits for the Program Trees in any year. In other words, the combination of the tree growth rate and the tree survival rate will determine the final multiplier factor that will estimate the appropriate level of the Program Tree benefits for any year. Given the age of the Program Tree from the tree planting date, the estimator will automatically multiply the energy, capacity and carbon sequestration benefit values of MATURE trees with the appropriate Tree Growth and Survival Rate FACTOR. Additional manual calculations are NOT needed.
In the event you have any questions and need any additional information about the methodology, please contact via e-mail the SMUD staff who was responsible for designing the Tree Benefit Estimator.