I wash at 60 if I possibly can, they come out cleaner and I do not have to use biological or souped up (with extra chemicals) detergents. I use a French soap based detergent that does not bring me, or my DDiL up in a rash.
I think whatever energy is used up heating the water to 60 is balanced by all the extra chemicals and processing needed to get washing hygienically clean at those low temperatures.
Favourite small treat when feeling blue or conversely a bit flush



