A kilowatt hour (kWh) is a unit of measurement for electricity; you'll probably see kilowatt hours written on the electricity meter in your back yard or basement. The specification kilowatt hours per year tells you approximately how much electricity an appliance uses each year.
By comparing the kWh per year of different appliances, you can find more efficient models. A top-load washer might use 450 kWh per year, for example, while a more efficient front-load washer might use only 150 kWh per year. To put this in perspective, in 2012 the average family used 500-1,250 kWh per month, according to the U.S. Energy Information Administration. More efficient appliances are better for the environment and can reduce your electricity bill.