Hot Yoga gets your heart rate up, while increasing your flexibility, and peace of mind. It's great for burning calories. I'm always floating afterward. Many studios have a karma class for a reduced fee that goes to charity, and many studios also let you trade cleaning duties for classes.
Don't try to scrub your yoga mat with soap and water. It is a large sponge, and you will never get the soap out. Don't try to go to a hot yoga class with a yoga mat that still has soap in it. You will find your feet sliding out from under you.