How much power am I really using?

[petrw1]

I know what I have for a power supply in each system.
But if they all were at capacity my power bill for PCs alone would be the whole bill.
Does anyone have a sense for how much power a PC typically daws?
For example an i5-750 or an i5-3570, both OC'd 20%. Fan, CPU and RAM probably non stop but Monitor is almost always off, and hard drive too. No GPU.

Or is there a device I can get to measure it?

Thx

[kracker]

Originally Posted by petrw1

I know what I have for a power supply in each system.
But if they all were at capacity my power bill for PCs alone would be the whole bill.
Does anyone have a sense for how much power a PC typically daws?
For example an i5-750 or an i5-3570, both OC'd 20%. Fan, CPU and RAM probably non stop but Monitor is almost always off, and hard drive too. No GPU.

Or is there a device I can get to measure it?

Thx

Kill-A-Watt for sure!

[chalsall]

Originally Posted by kracker

Kill-A-Watt for sure!

I agree.

You cannot measure the draw on a DC (direct current) feed without "being in the circuit".

An AC (alternating current) feed *can* be measured without being in the circuit, so long as you know the frequency and the voltage being used.

This is grade-school physics.

[sdbardwick]

Originally Posted by chalsall

You cannot measure the draw on a DC (direct current) feed without "being in the circuit".

Hall effect sensors would disagree.

[chalsall]

Originally Posted by sdbardwick

Hall effect sensors would disagree.

As always, I'm very happy to be corrected.

I was arguing from the perspective of the instrumentation most of us have available to us. Perhaps that was short-sighted.

A DC meter can only measure DC load when "in circuit".

Most electricians carry around with them a device which can measure the number of amps being carried through a single wire carrying AC -- importantly without having to break the wire, but only when encircling a single current carrying wire -- when the device encircles the bundled wires it measures zero (as it should).

Perhaps you could let us all know what hall effect sensors are available retail? I would sincerely be interested in knowing.

[Mark Rose]

Originally Posted by petrw1

I know what I have for a power supply in each system.
But if they all were at capacity my power bill for PCs alone would be the whole bill.
Does anyone have a sense for how much power a PC typically daws?
For example an i5-750 or an i5-3570, both OC'd 20%. Fan, CPU and RAM probably non stop but Monitor is almost always off, and hard drive too. No GPU.

Or is there a device I can get to measure it?

Thx

For a ballpark answer, take the CPU max TDP and add 10-20 watts for motherboard, RAM, fans, and PS inefficiency.

[chalsall]

Originally Posted by Mark Rose

For a ballpark answer, take the CPU max TDP and add 20-30 watts for motherboard, RAM, fans, and PS inefficiency.

That's not a measurement. It's an estimate.

A very important difference.

[fivemack]

Originally Posted by petrw1

I know what I have for a power supply in each system.
But if they all were at capacity my power bill for PCs alone would be the whole bill.
Does anyone have a sense for how much power a PC typically daws?
For example an i5-750 or an i5-3570, both OC'd 20%. Fan, CPU and RAM probably non stop but Monitor is almost always off, and hard drive too. No GPU.

Or is there a device I can get to measure it?

Thx

You can get a variety of in-line electricity meters; I own six. The i7/4770K box is 25W idle 90W flat-out, the Avoton is 20W idle 35W flat-out, the i7/4930K is 100W idle 160W flat-out 220W flat-out-with-GPGPU-on-top. The 48-core Opteron 6128 is about 300W idle and 550W flat-out.

[chalsall]

Originally Posted by fivemack

You can get a variety of in-line electricity meters; I own six. The i7/4770K box is 25W idle 90W flat-out, the Avoton is 20W idle 35W flat-out, the i7/4930K is 100W idle 160W flat-out 220W flat-out-with-GPGPU-on-top. The 48-core Opteron 6128 is about 300W idle and 550W flat-out.

Please correct me if I'm wrong, but this is "in the CPUs".

Measuring the total power draw on the DC rails is a little tougher....

[sdbardwick]

Fluke and other makers have a bunch of clip-on probes/meters. If they measure DC current via clip-on probe, then they are using Hall effect sensors.

An (expensive for casual hobbyist) example is the Fluke i410, which is just a probe and used along with your multimeter.

Of course there are cheaper units, like this one via Amazon.


Hall effect sensors are often used with magnets as a contact-less substitute for magnet/reed switch combinations (as the mechanical reed switch is limited in lifetime and response rate).

[petrw1]

Originally Posted by fivemack

You can get a variety of in-line electricity meters; I own six. The i7/4770K box is 25W idle 90W flat-out, the Avoton is 20W idle 35W flat-out, the i7/4930K is 100W idle 160W flat-out 220W flat-out-with-GPGPU-on-top. The 48-core Opteron 6128 is about 300W idle and 550W flat-out.

Thanks all but I think this is what I want....an inline meter.....and a few 48 cores :)