We have stood in the shade and felt it all along. Now, a new study has come along to prove it and equate it with energy savings. It documents the possible energy savings through the right placement of trees around a house. The study titled ‘The Value of Shade: Estimating the Effect of Urban Trees on Summertime Electricity Use’ says that trees placed on the west and south faces of a house in a hot area of California can cut back a homeowner's summertime electric bill by about $25 annually. Not impressed? Just multiply the small change with the number of houses in California. The numbers assume significance.

The study was conducted last year taking 460 single-family homes in Sacramento. The results declared on the 5th of this month prove that proper placement of shade trees does influence the carbon footprint. Sacramento was chosen because of the raging summers and the wide use of air conditioners, no doubt causing a large carbon footprint. The Sacramento Municipal Utility District is very active with its tree planting campaigns. Residents are entitled for up to 10 free trees per year through a program co-opted with the Sacramento Tree Foundation. Also, in 2007, the Sacramento Municipal Utility District gave away 16,000 free trees (at a cost of $85.00 a tree) to its customers. The district will recover this money in 26 years provided trees are planted on the west side of a house.

Geoffrey Donovan a research forester with the Forest Service's Pacific Northwest (PNW) Research Station is one of the authors behind the report along with economist David Butry of the National Institutes of Standards and Technology. He says,

"Because homeowners experience virtually none of the carbon benefits of tree planting, a subsidy to encourage tree planting seems warranted. Indeed, many of the benefits of urban trees have been shown to spill over to others in the community."

The conclusions of the study were -

• Placement of a tree is central to energy savings. The amount of the savings depends on the location of the tree.

• Trees planted within 40 feet of the south side or within 60 feet of the west side of the house will generate about the same amount of energy savings. This is because of the way shadows fall at different times of the day.

• Tree cover on the east side of a house has no effect on electricity use.

• A tree planted on the west side of a house can reduce net carbon emissions from summertime electricity use by 30 percent over a 100-year period.

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