To find out how efficient your machine is, there are several things to consider. First, there are two kinds of washer/dryer combination machines: vented and ventless. The first essentially works like a standard side-by-side washer and dryer. The washing cycle involves laundry that's whirled around in soapy water, rinsed, then spun with heated air. The generated steam leaves the unit, and your home, through a vent.
Of course, a ventless washer/dryer combo doesn't have a vent or exhaust shoot. It differs mostly in regard to how it dries clothes. A condensing chamber is cooled, and air in the drum (where the wet clothes are) is heated. When the drum spins around, this warm air retains moisture, which gets kicked through the condensing chamber. Here, the moist air cools and turns into water, leaving the machine through a pipe. Laundry can feel a bit damp even after the cycle is done. You can help maximize efficiency by not overloading the machine or by removing clothes after the dry cycle to finish drying them outside of the unit.
When it comes to overall efficiency, over the last 10 years, washers have become more efficient while dryer technology hasn't changed significantly [source: Consumer Reports]. This means that some combo units can be more energy-efficient than two separate standard machines.
The enhanced energy efficiency of combo units comes down to their reduced hot water usage and washer mechanics -- the stainless steel drum spins faster than ever (up to 1,000 rotations per minute) sucking more water out of the laundry. A family of four can save about $100 each year on laundry utilities using a combo machine, thanks to its reduced use of energy and water [source: NAHB Research Center].
So, ultimately, many washer/dryer combination machines can be counted as energy-efficient appliances. A handful of combo machines meet ENERGY STAR and Consortium for Energy Efficiency standards, and these models are among the most energy efficient. You can also look for a black and yellow EnergyGuide label. The Federal Trade Commission requires that all combo units display this sticker, which will tell you the machine's energy use. Keep in mind that this sticker only rates the unit's energy use against other compact, front-loading washing machines, not against the average capacity of top-loading machines.
For links to additional information on energy-efficient appliances, laundry and more, click to the next page.