The number of Americans willing to pay more for an environmentally friendly product has declined over the past five years by 13 percent, according to the "Survey of the American Consumer" by GfK MRI. And even fewer are willing to trade convenience for a product that's environmentally safe. Of those U.S. adults who did buy green in the last year, the top four purchases were lightbulbs, paper towels, laundry detergent and toilet paper. In Consumer Reports tests of these products, some have performed better than others. Here's what we found.

Lightbulbs. In the GfK MRI survey, almost one in five people had purchased energy-saving lightbulbs in the last year. That may indicate a growing awareness of the phaseout of inefficient incandescent bulbs. In Consumer Reports ongoing lightbulb tests, we've recommended many replacement compact fluorescent (CFLs), light-emitting diode (LED) and halogen bulbs. And as the prices come down, payback time does too.

Paper towels. All the green paper towels we've tested ended up in the bottom half of our Ratings. White Cloud Green Earth from Walmart led the pack of the green brands but scored only a 54 out of a possible 100. Its downfall was the absorbency test where it was a mediocre performer. Other so-called green versions did even worse. To learn more about the green claims, read our paper towel buying guide.

Laundry detergent. Seventh Generation Natural Superconcentrated powder was the only green laundry detergent that made our recommended list. Its brandmate Seventh Generation 2X Concentrated Natural liquid Free & Clear HE did not fare as well and other green cleaners fell further down the list. Worst of the bunch was Martha Stewart Clean, which makes environmental claims but scored only a 27 in our laundry tests.

Toilet paper. Our latest toilet paper tests included several green products. Trader Joe's Super Soft Bath Tissue, which is made of paper from responsibly managed forests, was very soft but did not score as well on our strength and tearing ease tests. Toilet papers made from recycled content fared worse. Strength was the shortfall with Seventh Generation though it excelled in other areas. Whole Foods' 365 Everyday Value and CVS's Earth Essential were at the bottom of our Ratings because of their roughness and middling strength and tearing ease. But they did offer excellent disintegration, a plus for your pipes.

There was one finding from the survey that bodes well for the future—the willingness of consumers aged 18 to 24 to give up convenience or pay more for green products has held steady over the past five years. And more than half of them recycle the products they do buy.