Admit it. There are a bunch of you out there who still wash your clothes in hot water. Don't worry, I'm with you. But this just in: Stop. Use cold. Washing with hot wastes money, energy, and is bad for the environment.
First, being poor means I don't exactly have the means to separate my precious delicates from the rest of my laundry. That's incidental. I would if I could, trust me. I have an addiction, you guys. I like separating and knowing on some base level that my favourite pair of boxers is especially clean. And the truth is that, yes, in a perfect world hot water is better at getting things clean. It's physics.
But f**k physics. For one, the expense and environmental toll inherent in any load of laundry outweighs the benefit of separating your clothes out for a nominally cleaner set of undies. According to the New York Times:
About three-quarters of the energy use and greenhouse-gas emissions from washing a load of laundry come from heating the water - a practice that, scientists say, is often wasteful and unnecessary.
For another, the industry is starting to catch up. Different companies, Tide's Procter and Gamble included, have come out with a number of cold water alternatives that wash your clothes more than satisfactorily and they're only improving. And many manufacturers are working on high-efficiency machines that better utilise cold water. Really, the greatest obstacle to us saving money is... us.