PSU AC input question

[lazi]

I'm currently looking for a new PSU to complete my second computer, which it will be configured for gaming applications. As I was reading the power specs I noticed in the AC input the amps was high to the watts generated.

 

For the 1000watt supply, it shows 100-240v ~ 13amps. In my house I use 120 volt outlets. If I use the math formula to find out the amps from watts I get a different answer.

 

1000w/120v = 8.3amps.

 

So if I used the 1000watt supply will it draw in 8.3amps for the 120v or will it use the 13amps that is listed on the label?

[FEAR6655]

You are not taking into account the efficiency of the PSU. We'll assume the PSU has 80% efficiency so when you are drawing 1000w from the DC side, 1200w is actually being drawn from the AC outlet, therefore 1200/100 = 12A. However, the efficiency at full load is unlikely to be 80%, so working backwards from 13A we get 1300w from AC at 100% load, we get an efficiency of 77%. The 13A consumption would only occur when consuming 1000w DC on a 100V supply line. This is highly unlikely and the PSU will only consume AC what the PC is consuming DC plus the power lost through efficiency. For example if you components are using 367w DC then the AC current would be somewhere around 3.7A at 120v (367w @ 80% = 440w/120v)

[lazi]

Ah I see. I'm not sure the exact number of watts this PC will draw. The PC has the new Nvidia GTX 295, Intel i7 CPU, 6gigs of RAM, and 1 hard drive. My main concert was with those components will my power bill jump significantly?

[FEAR6655]

tThe newer componenrs are quite energy effiecient when idle (I don't know about you but my PC spends most of its time idle). Unless you are running every component at 100% load for long periods of time, I don't think you willl notice it.