simple power consumption question

[heffer]

If I used a 700W power supply for my new computer, but my new computer only needs 300 watts to run properly, then is it actually using 700 watts or just 300 watts? i hope that makes sense.

[peterhuang913]

It should use less than 700W. But you can't be sure unless you measure it.

[nitestick]

power supplies always consume more than the sum total of the components they are powering due to the inefficiency of their workings. it should not be running at maximum power unless the components are drawing that much power.

[heffer]

so if my computer only needs 300 watts, then would I save money on my electric bill by using a 500W PSU rather than a 1000W PSU? or would my bill be the same amount?

[nitestick]

nope, the only thing that would matter would be the efficiency of the power supply. if they are both say 80% efficient then they would both consume 375w of power.