I use a Hoover with onboard heater and it works very well for me. I don't ever purchase the Hoover carpet cleaning solution - it just made my carpet feel sticky. For the two wool rugs I have, I use 1 cup of distilled vinegar and fill the rest with water. For the light carpeting, I use a mixture of a little dissolved oxyclean plus X-O (this is an enzyme cleaner to take care of pet spots and kid spills) plus water. Works great. The onboard heater really makes a big difference. My previous cleaner did not have one and did not clean nearly as well.

As to liquid use - you control the amount you choose to use. The liquid is only sprayed when you hold the trigger. None of the models available have a huge cleaning solution or dirty water tank. You would have to go with a commercial model for that.