How exactly does a power supply draw power?

[TehCaucasianAsian]

So, I have a CX500 in my build. So it can draw 500W of power maximum. According to PCPartPicker, my entire rig will consume about 350W of power. My question is what exactly does that mean? Am I drawing 350W of power every second? Every minute? Every hour? I don't look at my parent's electric bill, and my computer isn't a separate payment so I can't just do the math and find out that way. Please let me know how a PSU draws power over tme

 

[Dark Lord of Tech]

Your computer will only draw the power it needs to run efficiently.

http://www.xbitlabs.com/articles/coolers/display/system-wattage.html

http://hexus.net/tech/tech-explained/psu/32105-psus-power-supply-units/

 

[USAFRet]

The PSU supplies power to the components as they need it. At idle, you'll be drawing a fraction of that 350W. Under load (gaming/Prime95/coin mining), it will supply more power as needed.

Looking at an electric bill, you'll see it in kW/hour. Kilowatts per hour, for the whole house.
At full load on your PC, you have the equivalent of 3 100W lightbulbs on.

 

[13thmonkey]

power is sold in units called KWh, i.e. 1000W in an hour. So a PC drawing 350W from the wall will use 0.35 KW every hour, so if it is on for 3 hours, running at full speed, it will use 3x0.35 = 1.050KWh, i.e. approx 1 unit of electricity every hour. In the UK this costs about £0.10/unit so running for 3 hours cost £0.10.

 

[USAFRet]

In the UK this costs about £0.10/unit so running for 3 hours cost £0.10.

So for actual numbers, running that PC full tilt 24/7 adds £24/month to dads electric bill.
Unless you're coin mining 24/7, the PC is not running that hard ALL the time.

 

[13thmonkey]

don't know what country he is in though, and therefore the unit costs.

 

[USAFRet]

don't know what country he is in though, and therefore the unit costs.

Right. I just put that there for a 'monthly' look as to what might happen to dads electric bill.

 

[13thmonkey]

Absolutely, it's really useful to know, as many people can't figure it out.