A regular washer depends mostly on water and the physical agitation of laundry to do its cleaning. A steam washer, by contrast, takes advantage of the penetrating power of steam to increase its cleaning efficiency and sanitizing capability. The advantage of steam washers over conventional washers is not, however, always clear-cut.
Washers equipped with a steam cycle use heat to generate steam and then inject that steam into the machine's tub during the wash cycle. In theory, the heat of the steam makes clothing fibers more absorbent so that water and detergent can more effectively penetrate the fabric and lift out stains. A 2008 Consumer Reports test suggested that steam cycles do, in fact, result in slightly better cleaning, but the report also noted that some more expensive steam-equipped washers excelled at stain removal even using their regular wash cycles.
Because a washer's steam cycle relies more heavily on the cleaning power of steam than that of water and agitation, a typical steam cycle uses much less water than a regular wash cycle. Some steam machines marketed specifically as water-saving models may use up to 9 fewer gallons per cycle than comparable conventional models. If it uses less water, a washer uses less energy to heat the water, although the electricity required by a long steam cycle may eat into a steam washer's advantage in terms of energy efficiency.
The high heat introduced during a washer's steam cycle may be effective at killing dust mites and some kinds of bacteria, and many steam washer models are equipped with steam cycles specifically intended to eliminate allergens. Washers that meet the NSF P172 specification are guaranteed to remove 99.9 percent of certain common bacteria and allergens and not transfer allergens from one load to another. NSF certification -- granted by the independent testing lab NSF International -- is common among steam washer models, but some conventional models use high-temperature water in their sanitizing cycles to meet the NSF standard.
Steam is often considered to be a luxury feature that adds substantially to the cost of a washer. Steam cycles are typically part of the feature set of high-end washers, and some steam-equipped models cost close to $2,000. However, some lower-end steam models cost less than $1,000 and overlap in price with conventional washers.
Fabric and Machine Longevity
In theory, a steam cycle that uses less agitation than a conventional cycle will be gentler on fabrics, but there's not much evidence that steam washers significantly extend the life of fabrics. Steam washers in general also don't seem to be prone to more maintenance problems than conventional washers, and both types of washers are covered by comparable manufacturers' warranties.