Question Regarding Watt Usage

I am currently getting information together about a new system I want to build. I currently use a 620W Enermax Liberty PSU. I have 7 120mm Fans, 6 80mm Fans, 4 hard drives, 2 DVD drives, along with 2 fan controllers. I also have a video card that uses power. My question is how can I find out how much power everything requires? The CPU, motherboard, and GPU requirements I can find rather easily. But the fans, DVD drives, and hard drives I'm not sure about. I want to determine how much total power my system is using and whether I might need a larger PSU. I'd like switch to water cooling, but this will obviously require more power. Any help or suggestions is appreciated.

Thank you.

 

Thats a great link. Thank you very much.

 

There's a basic wattage calculator here:

http://www.jscustompcs.com/power_supply/

There are others..... have a Google.

I think that Enermax will have you covered pretty comfortably unless you're going for very serious multiple graphic card setup.

 

I can tell you right up front, you don't need a larger P/S!

 

I am close to needing a larger one. I don't need it, but I am close if I rate everything at 100% load which just doesn't happen.