As others have said the big machines that you can hire from supermarkets and dry cleaners are very heavy and cumbersome to use, especially in average size rooms unless you can empty it completely.
We bought the smaller Rug Doctor domestic machine and it's marvellous, well worth the money. Much lighter and easier to manoeuvre, and it cleans really well and leaves carpets almost dry. The Rug Doctor liquid can be a bit pricey and difficult to get where we live, so I buy a similar product from Amazon and it's actually better. We do our bedroom and stair carpets once a month (we have a dog) and it keeps them fresh and soft.