Estimating System wattage

[Michael Semcheski]

On Fri, Aug 22, 2008 at 1:40 PM, Christopher Snook <csnook at redhat.com> wrote:
> You only need massive power supplies in a desktop if you're running high-end
> video cards or something else that needs separate power inputs.  Enjoy your
> very long UPS runtime.

In my experience, peak power usage can be much higher than the average
power usage.

e.g., at boot time the system uses lots of power to spin up the drives
and fans.  Once their rotational velocity is established, power usage
can drop to 50% of peak and stay down.

The other line of reasoning I've heard for buying an over-sized power
supply is because running the power supply closer to capacity will
shorten its life.  Also, power supplies may be more efficient running
at a fraction of their maximum rated capacity.  i.e., a 200 watt power
supply delivering 150 watts of power is less efficient than a 450 watt
power supply delivering 150 watts of power.  Maybe someone who really
knows can respond to this point.

Mike