Do window shades reduce heating and cooling costs?

Yes, by closing the blinds, you keep direct sunlight out of your rooms and reduce unwanted solar heat gain.

During cold nights, heat is lost through windows. Closing the blinds adds some insulation to the windows, reducing heat loss. Mount them as close to the glass as possible to create a sealed space that minimizes heat gain. This will allow you to use your heating and cooling system more efficiently and to save energy.