The US Department of Energy has a helpful guide to buying energy efficient home appliances on their website here.  "This easy-to-read guide may help you understand how appliances are rated for efficiency, what the ratings mean, and what to look for while shopping for new appliances."

For example, advice on buying clothes washers:  "[l]ook for the EnergyGuide label that tells how much electricity, in kWh, the clothes washer will use in one year. The smaller the number, the less energy is uses. ENERGY STAR clothes washers use less than 50% of the energy used by standard washers."

There is information for buying:  room air conditioners, programmable thermostats, water heaters, dishwashers and more.  There are also links to Energy Star products and how to buy energy efficient home electronics.