Cold fill machines are pretty much the norm now, built by manufacturers to A: Save money in the build process (less components) B: Achieve the energy efficiency rating (AAA, AAB etc) Having a hot & cold fill machine means that water from your central heating is added (depending on the programme / temp required) that has already been heated by a more efficient system than the one in a machine ... however if it is too hot then cold will have to be added to reduce the temp ... therefore less energy efficient than cold fill only ... however the ratings are mainly achieved by having lower temp washes over a longer period of time ... hence longer washes despite advancing technology ... in short, no real advantage or disadvantage ... modern top end detergents dissolve very well in cold water (powder & tablets at least, however liquids are one of the main reasons for the increase in smelly machines & mouldy door seals in the last 5 years ... none of them contain any bleach to kill off the remaining bacteria ... (IMHO