To anyone suffering the misery of a Northern Hemisphere winter, a baking hot summer seems a lifetime away.

But a new study from the US Forest Service's Pacific Northwest (PNW) Research Station in Oregon has shown that planting a tree to the south or west of a house can cut electricity bills by $25 (£17.50) a year.

The shade from a leafy tree cuts the heat absorbed by windows and walls, reducing the need for air conditioning when the sun puts his hat on.

Shady business

The study, carried out in the sunny city of Sacremento, California, found that positioning the tree was crucial.

For best results, trees should be planted within 40 feet of the south side or within 60 feet of the west side of the house (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.

In total, the study calculates that 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.

Of course, you'll have to site your solar panels a little more carefully...