Dishwashers have become much more efficient over the last decade, with new EPA Energy Star-rated machines using as little as three gallons per load. But like any appliance, the benefits it provides will evaporate unless it is operated efficiently--and that means higher water bills, higher energy bills and more wear and tear on your dishwasher. But should you replace your old standby?

The biggest factor to consider is whether your current dishwasher is Energy Star-certified. Energy Star models are 41 percent more efficient than the minimum federal standards. They consume less hot water, have energy-efficient motors and use sensors to determine the length of the wash cycle. If your dishwasher was manufactured before 1994, you'll save more than $30 a year with a new Energy Star-certified machine. When shopping for a new dishwasher, choose one with a "light wash" or "energy saving" cycle, and expect to hang on to it for about nine years, suggests the National Association of Home Builders. And when your dishwasher has expired, do replace it, since hand-washing dishes generally uses more water than dishwashers do.