Re: [OT] Help with power usage calculation

[Jim Noble <yahoo-groups@xxxxxxxxxxxxxxxxxx>]

Alex Monaghan wrote:

> As the electricity bill is in KW/h how would I convert usage when all
> I have
> on the product specs is a single figure (for example my monitor is
> rated at
> 150W and 5W on standby). If I can get to the same unit figure as the
> electricity bill, I can then work out actual £££ cost of having each
> device
> on.


I suspect your bill is in kWh. Multiply the power consumption of your
appliances by time to get the same units (ie 150W for an hour is 0.15kWh).

>
> For something like a PC where the PSU is rated at 300W (for example),
I
> guess it doesn't constantly draw 300W, could the usage be calculated
> easily
> without actually plugging in a device to measure consumption ?


Not really.

> If I can do this, I can then work out how much cheaper it would be to
> run an
> LCD and provide full justification to SWMBO for replacement of
monitors.
> Maybe even justify some other new toys on this basis if I'm lucky :)


Unless you have a lot of very large CRTs which you intend to replace
with one LCD, I suspect you'll need another excuse :-)

> How about calculating the use of things like power transformers (all
they
> say is the output voltage at X amps)


Unless they are 100% efficient (Switch mode psus might manage
80-90%...), you'll need to at least measure the current going in...

Jim