Dear Jim: I need to replace my old refrigerator-freezer with a more modern and efficient one. I have plenty of room in my kitchen, but I am not sure what configuration to get. Which ones are most convenient and efficient? – Penny L.

Dear Penny: Any new refrigerator-freezer you purchase will use less than half as much electricity as your old one, but some designs are inherently better than others. To get an Energy Star rating (www.energystar.gov), new refrigerators must now use 15 percent (it used to be 10 percent) less electricity than the federal energy efficiency standards.

Your budget will be the primary factor in determining what design of refrigerator you select. For a typical size model, prices can range from about $500 for a top-freezer model to more than $5,000 for a built-in model with all the bells and whistles. The difference in annual electricity usage is about $20.

A top-freezer model is the most popular and efficient configuration. The primary advantage is easy access to the freezer and the highest percentage of usable interior space. These use a single compressor for lower cost and the cold freezer air naturally drops to keep the refrigerator portion cool.

Other configurations, such as a side-by-side, require more exterior space for the same interior space. To make things worse, the usable interior space may be considerably less than the advertised amount. Much space may be used for hardware, shelf brackets and unusable corners. Side-by-side models are convenient to use and the narrower doors require less space when opened.

If you do not often use frozen items, a bottom-freezer model raises the refrigerator portion up higher for easier access. Some new designs use a side-by-side refrigerator with narrow doors above the freezer compartment.

Built-in models are the most attractive, but also the most expensive. They are tall to match the cabinet height and to provide adequate capacity since they are more shallow to match the cabinet depth.

To maintain the proper refrigerator (37 degrees) and freezer (0 degrees) temperatures, a two-compressor model is best. It has two totally independent cooling systems for precise temperature control in each compartment. In a one-compressor model, the compartments are connected.

Digital temperature controls and readouts are more convenient than just turning a knob and waiting to see if the orange juice freezes. New glass door models are also convenient and allow you to graze without having to hold the door open and waste electricity. Through-the-door water and ice dispensers are a plus, but they are a frequent cause of service calls.

The following companies offer refrigerator-freezers: Elmira Stove Works (800) 295-8498, www.elmirastoveworks.com; Equator Corp. (800) 776-3538, www.equatorappliances.com; Heartland Appliances (800) 361-1517, www.heartlandapp.com; Maytag (800) 688-9900, www.maytag.com; and Sub-Zero Freezer (800) 222-7820, www.subzero.com.

Send inquiries to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.