Madrid Barajas

At the end of my little Southern Europe trip at the end of June i am planning to spend about 16 hours at Barajas instead of getting a hotel on my last day when I come back from Granada, mainly because i am rather sure I will be skint by the end of my shoe-string budget tour.

So, i just wanted to know how are the facilities at Barajas? Is it possible to spend my allotted time there or should i look into getting some extra money to get a hotel in Madrid city?

many thanks.