I use an old-style round thermostat to control the heat in my home but am considering switching to a new digital programmable model. Will this type of thermostat help me save money on my utility bills?

Programmable thermostats can cut your heating and cooling costs by up to 20 percent by automatically raising or lowering temperatures at night and when you're away from home.

"Programmable thermostats can save significant energy, but only when programmed correctly," says Maria Vargas, a spokeswoman for the U.S. Environmental Protection Agency. But, says Vargas, "We've found there's a margin for error [in using thermostats] that leads to energy waste." Indeed, many people assume that no programming is needed for thermostats, Vargas adds. The EPA is proposing an educational program and will work with the industry to make thermostats friendlier to use.

Manufacturers have taken some steps to make programmable thermostats less daunting. The best models have built-in energy-saving programs, eliminating the need for you to create them from scratch. But you'll still have to set the time, date, and the system your thermostat controls. Odds are, you'll also want to tailor programs to your schedule.

Use our Ratings and Quick Picks (available to subscribers) to find an easy-to-program model that’s right for your home. (For instance, most models work with most heat-pump systems, though only a few work with multistage heat pumps.) Then consider these shopping points before buying:

Pick a model with the programs you want. If you have a predictable, consistent schedule—you leave for work at the same time on weekday mornings and return home at the same time in the evening—the best thermostat for you might be a weekday/weekend model, which offers one energy-saving program for weekdays and one or two for Saturday and Sunday. Models with different programs for all seven days are often pricier, though several cost no more than simpler models.

Look for convenience. Thermostats with a touch-sensitive screen (footnoted in the Ratings) can be easier to use than those with an array of buttons. Models that switch automatically between heating and cooling are also the best thermostats in areas where days are warm and nights get below freezing, as are those that clearly show whether they're running the heat or air-conditioning. While most have batteries that save at least part of a customized program after a blackout, some save all of it. One, the Lennox SignatureStat (shown), works completely off home wiring yet can fully save programs

Consider the installation. Most programmable thermostats attach to your heating or cooling system with as few as two low-voltage wires, making installation easy. Just be sure to check which wire goes where before removing your old one. See our primer on installing a thermostat.

Essential information: Read our expert advice for 10 easy ways to save hundreds of dollars on energy costs at your house, including installing new windows.