Saying you use hot water to clean a house does have certain marketing advantages. You wash your dishes in hot water, you take a shower with hot water, doesn't it make sense that hot water cleans better? Most home owners will agree. It's just another way of separating yourself from others.
I would imagine that in the summer time it doesn't much matter. In fact, if you're heating your water to over 100 degrees I bet it's killing your house wash soap, especially if you're downstreaming. It can allow you to clean further into the winter though. Heating the water up to about 80 would help with cleaning and it wouldn't burn too much fuel.