Consumer Reports’ tests of laundry detergents over the years have shown there’s little performance difference between powders and liquids: It’s simply a matter of personal preference.

Yet there may be a world of ecological difference among detergents depending on whether they contain harmful chemicals. Nonylphenol ethoxylates, also known as NPEs, are compounds used as surfactants (dirt removers) in some detergents. Recognized by the U.S. Environmental Protection Agency as toxic to aquatic plants and animals, NPEs are banned in parts of the European Union.

But some detergents made for the United States still contain these chemicals because they cost less. Those savings may not wash, however, when you consider that many products with NPEs performed worse in CR’s tests than those with more environmentally friendly surfactants.

We tested some three-dozen detergents for their ability to remove stubborn stains including chocolate ice cream, grass and red lipstick from cloth swatches. We also looked at how well the products prevented dirt in the wash water from resoiling clothes, and whether they kept dyed items from bleeding with others.

Several of the detergents were labeled “HE” for high efficiency. Manufacturers of front-loading washers recommend HE detergents for their machines because the products are made to work with smaller volumes of water. It’s not as clear-cut for top-loaders, so check the owner’s manual. Using the wrong type of detergent can lead to over-sudsing or poor results.

Our top-rated product overall was an NPE-free HE detergent called SA8 with Bioquest – a powder that is available online (www.quixtar.com) from the company formerly known as Amway. It was the only detergent CR tested that excelled at all our measures, yet at 61 cents per load, it was also the most expensive. (That price doesn’t include shipping, which can cost $5.75 to $20.) For less than half the cost of SA8, Gain HE liquid (28 cents per load) performed nearly as well across the board. Other notable high-efficiency detergents included Kirkland Signature Ultra 38722 liquid (at 12 cents per load, from Costco, it’s a CR Best Buy) and Method Fresh Air 3X Concentrate HE liquid (22 cents). All are NPE-free. Although it contains NPEs, Sears Advanced Formula Plus with OxiClean Ultra HE 9820 powder (12 cents) performed very well in the tests.

If you have a top-loading washer or require a conventional detergent, Tide with Febreze Freshness liquid (27 cents) and Great Value Ultra Glacier Breeze liquid (at 12 cents per load, from Wal-Mart, it’s a CR Best Buy) provide sparkling results at a comparatively low price. Both are NPE-free. If you want an NPE-free powder for your conventional washer, consider Tide with Bleach (24 cents). It performed much better than the cheaper (11 cents per load) Sears Ultra Plus Stain Fighting Formula 9835 powder, which does contain NPEs.

While CR tested several two-in-one products that combine detergent and fabric softener, none were recommended because regular detergents paired with separate softeners outperformed them.