I raised this question some time ago on AB. My wife and I had just returned from visiting our daughter in North Carolina where we discovered that she washed her clothes on the COLD setting of her washing-machine, using cold-water detergent which is a routine item on US supermarket shelves. Her washed cothes were as clean, fresh and soft as if they'd been washed in hot water.
We thought we'd try it when we got home but could find no cold-water detergent here. I e-mailed Proctor & Gamble who make the cold-water Tide in the USA who replied to say that they do not market it in UK or Eire. They gave no reason.
I agree that it would effect a tremendous saving in energy if everyone did it except for very soiled or contaminated clothes, but no-one seems interested. I wrote to BBC Radio 4's 'You and Yours' which deals with such things but they didn't even reply. Please let us know if you have any ideas for promoting the idea.