For a month before Xmas I disconnected my propane water heater and used the immersion fitted into my fresh water tank to heat my water I was cleaning with hand hot water ( so hot you could just about hold your hand in it ) this cleaned well, I think most people who talk about cleaning with 'hot' water are referring to water at this sort of temperature, in this temp range you can touch the QC.
I think the big difference comes when you go higher, when I use my heater the QC can burn your arm when you accidently touch it. this heat coupled with a high flow of water ( big jets in your wand) and a quality detergent makes cleaning really soiled carpets a lot easier.
Someone asked what difference a detergent makes as it only touches the carpet for a second but it's about lots of little differences added together to make a big difference. The coach for Team Sky the cycle team said all he looked for was a 5% improvement if he could make a a small 5% improvement in 4 different areas he would end up with a 20% difference....and that's what makes a winning team.
It's the same with cleaning carpets all we need is lots of small improvements in how we clean to make a big difference.
Ps: if you think 5% is not worth bothering about..... Usain Bolt won the 100m by being 0. 003% better than the person who came second
