Plant trees. Save electricity.

With all the talk of climate change and trying to cut down our carbon footprint, scientists this week have come up with evidence of a new way to help cut down on electricity bills - the solution may be as simple as planting some trees.

Two researchers from the States, David Butry of the National Institute of Standards and Technology and Jeffrey Donovan of the U.S. Department of Agriculture, have conducted a study looking at how planting trees around your house can help shade it in summer and reduce the need to switch on air conditioners. We all know that trees provide shade and a nice spot to sit under in the summer but this is the first wide-scale study to investigate whether this can translate into significant energy savings in the home. Butry and Donovan studied 460 homes in Sacramento during the summer of 2007 - they looked at what trees were growing around the house and then linked this to the energy bills of each household.

They found that planting trees on the west and south sides of the house decreased summer electricity use, by an average of 5% a year, while trees on the north side of houses actually increased the use of electricity and those on the east had no effect. Fast-growing trees work better than smaller, slower growing species. They worked out that a London Plane tree planted on the west side of a house could reduce carbon emissions from air conditioners by an average of 30% over 100 years.

And of course trees have the added benefit that they not only shade houses but they absorb and lock away carbon dioxide from the atmosphere too. This study sounds very promising and the authors are keen for researchers in other regions of the world to see if they find a similar pattern.