How much sleep do cats need?

We all know that cats and kittens are famous for the amount they sleep but how much do they actually need?
I'm thinking kittens need to sleep more for development and to recharge as they are so active.

As humans we need a recommend amount of sleep to be able to function normally and depriving our body of sleep will cause health problems, but what about cats?

I have done a bit of googling but didn't come up with much that answers this question specifically.

Any thoughts?

I read somewhere that cats do not really sleep the way we do. Unless they're drugged or maybe sick, they're wired in a way that they sleep "with one eye open".  They will wake up to any sudden change in their surroundings.Their batteries are being charged but slower than us during naps. 

Probably a lot of people will disagree and say that their kitties are comatose during sleep but I actually believe that they choose to act that way so we won't bother them.   

Personally I think it's more like "one ear open". Every cat I've known would wake up at the slightest sound. That is, until my Crumbs went deaf. She sleeps like the dead, now, and it can be difficult  to wake her up.

I read somewhere that most cats spend about 20 or so hours a day sleeping. Bored cats may sleep more than others. Some breeds may sleep less than others. I swear my Aby never ever sleeps I have never once seen him curled or stretched out for a nap or just to rest. He's always zooming around at top speed.

I have been doing some reading and although I still have not found an answer to my specific question I did come across some interesting articles on the sleep cycles of cats if anybody would like to read.

http://www.pets4homes.co.uk/pet-advice/the-sleeping-habits-of-your-cat.html

http://www.intropsych.com/ch03_states/rem_sleep_in_cats.html

LTS3 said:

I read somewhere that most cats spend about 20 or so hours a day sleeping. Bored cats may sleep more than others. Some breeds may sleep less than others. I swear my Aby never ever sleeps I have never once seen him curled or stretched out for a nap or just to rest. He's always zooming around at top speed.

Click to expand...

This sounds familiar, it is really rare to catch any of mine sleeping, only when I heat fireplace they seem to climb near ceiling and form fur ball size of 5 cats, but any other time they just run around.