Hello,

I run a number of computers at home, and was wondering how much
electricity each one consumes. Is there some kind of device that can be
attached between the PC and the wall outlet to measure power
consumption?

Kind regards,
Herminio Gonzalez

On 26 Jan 2005 06:32:13 -0800, "Herminio Gonzalez"
wrote:

Hello,

I run a number of computers at home, and was wondering how much
electricity each one consumes.

About (finger in air) 200-500W (depending on the CPU spec, number of
drives and monitor type) ;-)

Is there some kind of device that can be
attached between the PC and the wall outlet to measure power
consumption?

Maplin do one ..

http://tinyurl.com/3l6hm

All the best ..

T i m

Thank you T i m, that's just what I was looking for!

Aniseed wrote:
Thank you T i m, that's just what I was looking for!

It's likely to be significantly (double the real reading) inaccurate,
the one I got from maplin is.
It works fine on simple loads like motors/heaters.

In practice, you can look up all the figures on websites.
2-300W is unlikely.

I measured my server (12 drives spinning, 1.3G duron) at around 150W.

That's discouraging. So according to your post, there's an error of a
FACTOR OF 2? How could one know what the real power consumption is...
Maybe I can calibrate it somehow, using devices with known power
consumptions. But I can't think of any such devices...

Aniseed wrote:
That's discouraging. So according to your post, there's an error of a
FACTOR OF 2? How could one know what the real power consumption is...
Maybe I can calibrate it somehow, using devices with known power
consumptions. But I can't think of any such devices...

Unfortunately not.
The meters (the cheap ones, the maplin and Lidl 6.99 ones) work out the
current by measuring the voltage/current several times per cycle.
Unfortunately, the lowest cost is got by reducing 'several' as much as
possible.

For things like heaters, or motors, you can almost trivially get a pretty
good reading of power and power-factor (amount current is leading or
lagging voltage) with just 3 or 4 samples per cycle.

This is because the current they draw is a nice sine wave.
Many PC (and other switched-mode PSUs) unfortunately have significant
very fast variations in current.
So, the meter misses these changes, and assumes that the power supply is
drawing a higher current than it should.

It's basically a similar problem to trying to join up the dots.
If you've got lots of dots, then you can make a nice smooth curve, without
worrying about the shape of the curve you make being different from the
intended one.
As you reduce the number of dots, eventually you get to a stage when
you're guessing.

More expensive meters should do better, unfortunately, determining how much
goes into the electronics is hard.

In an earlier contribution to this discussion,
T i m wrote:

On 26 Jan 2005 06:32:13 -0800, "Herminio Gonzalez"
wrote:

Hello,

I run a number of computers at home, and was wondering how much
electricity each one consumes.

About (finger in air) 200-500W (depending on the CPU spec, number of
drives and monitor type) ;-)

Is there some kind of device that can be
attached between the PC and the wall outlet to measure power
consumption?

Maplin do one ..

http://tinyurl.com/3l6hm

All the best ..

T i m


And if you buy it in the next couple of days, it's half price!
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

"Herminio Gonzalez" wrote in message
oups.com...
Hello,

I run a number of computers at home, and was wondering how much
electricity each one consumes. Is there some kind of device that can be
attached between the PC and the wall outlet to measure power
consumption?

Kind regards,
Herminio Gonzalez


Cheap power consumption meters are occasionally available for around £5 from
supermarkets such as Lidl or Aldi and also on ebay.
As a guide to consumption, a typical PC with an Athlon 2100 cpu, single HD,
average graphics card takes about 75W when idle, rising to about 140W with
full CPU load.
You need to add-on the consumption of your monitor,this may be available
from the manual or label on the monitor itself.
Older PCs with 300-400Mhz (AMD K6) cpu can use on average about 50W.
As the CPU power consumption is an important factor - it may be interesting
to read this CPU power consumption comparison -
http://www.silentpcreview.com/article31-page1.html

Dave

Sure, its possible to look up what one's CPU consumes, but there are
several hardware and software components drawing power, and it quickly
becomes difficult to know how much is really being consumed.

I'm particularly interested in the consumption of a lighlty equipped
PentiumPro machine which is on all the time, no monitor. It is
passively cooled, and the heatsink feels quite cool to the touch, so i
am hoping it is below the 50W mark.

I also have a P4 1.8GHz machine with 2 HDDs and a 21" CRT, I'm curious
to find out how much it really consumes, and how it compares to the
value from manufacturer's specs.

Herminio

Aniseed wrote:
Sure, its possible to look up what one's CPU consumes, but there are
several hardware and software components drawing power, and it quickly
becomes difficult to know how much is really being consumed.

I'm particularly interested in the consumption of a lighlty equipped
PentiumPro machine which is on all the time, no monitor. It is
passively cooled, and the heatsink feels quite cool to the touch, so i
am hoping it is below the 50W mark.

I happen to know this one!

I for about a year, I ran 3 Pentium Pro 166 (overclocked to 240Mhz)
motherboards, 3 hard disk drives, 3 ethernet cards on one 145W power supply.

I measured each motherboards DC usage as around 40W, with the CPU going
flat out. (mp3 encoding)

None of them ever crashed in about 3 years total run-time (adding up all
the motherboard times)

"Aniseed" wrote in message
oups.com...
Sure, its possible to look up what one's CPU consumes, but there are
several hardware and software components drawing power, and it quickly
becomes difficult to know how much is really being consumed.

I'm particularly interested in the consumption of a lighlty equipped
PentiumPro machine which is on all the time, no monitor. It is
passively cooled, and the heatsink feels quite cool to the touch, so i
am hoping it is below the 50W mark.

I also have a P4 1.8GHz machine with 2 HDDs and a 21" CRT, I'm curious
to find out how much it really consumes, and how it compares to the
value from manufacturer's specs.

Herminio


I have measured the consumption of an old machine fitted with a 400Mhz amd
cpu at between 40-60W and a Cyrix "300" machine at 38W - these machines have
large heatsinks with a very slow fan (at 5v) and don't produce much heat.
Your cpu may take more power - maybe as much as a Duron 800-900Mhz - so may
be worth checking further - see
http://www.geek.com/procspec/intel/pentiump.htm

For the best power efficiency - consider getting a Via EPIA board (various
built-in cpu options 500-1000Mhz).

I suspect the 21" CRT uses a lot of power too.

Dave

"logized" wrote:

"Aniseed" wrote in message
roups.com...
Sure, its possible to look up what one's CPU consumes, but there are
several hardware and software components drawing power, and it quickly
becomes difficult to know how much is really being consumed.

I'm particularly interested in the consumption of a lighlty equipped
PentiumPro machine which is on all the time, no monitor. It is
passively cooled, and the heatsink feels quite cool to the touch, so i
am hoping it is below the 50W mark.

I also have a P4 1.8GHz machine with 2 HDDs and a 21" CRT, I'm curious
to find out how much it really consumes, and how it compares to the
value from manufacturer's specs.

Herminio


I have measured the consumption of an old machine fitted with a 400Mhz amd
cpu at between 40-60W and a Cyrix "300" machine at 38W - these machines have
large heatsinks with a very slow fan (at 5v) and don't produce much heat.
Your cpu may take more power - maybe as much as a Duron 800-900Mhz - so may
be worth checking further - see
http://www.geek.com/procspec/intel/pentiump.htm

For the best power efficiency - consider getting a Via EPIA board (various
built-in cpu options 500-1000Mhz).

I suspect the 21" CRT uses a lot of power too.


Hi again,
Yesterday I recieved one of the Maplin Power meters in the post. It is made in
Taiwan, by Prodigit Elecronics Co Ltd. Its of reasonlably good quality build,
given the price.

I've tried it out on stuff around the house. After much bending over plugging
and unplugging things, I've acquired a list of results and a backache. If
anybody is curious, here is what I found out:

monospace font please
Appliance: Reading:
Kettle rated at 1800-2200W 1980W
Desklamp with 60W bulb 58W
PIII Dell Laptop 20W idle
PentiumPro 200MHz, 1HDD 40W idle
Athlon 1.4GHz, 1HDD 90W idle, 105W runing sims2
Pentium IV 1.8GHz, 2HDDs 75W idle, 100W running hl2
22" Iiyama CRT 5W standby, 70-100W on
Lower back Light throbbing
/monospace font please

I can see that the device has correctly measured the kettle and desklamp,
because the reading I get matches their power rating. However I don't know how
accurately it is measuring the various computers and the CRT monitor. I hope it
is accurate, because I was pleasantly surprised to see that the monitor
consumes about 75W when displaying my windows desktop, I thought it would be
higher.

However:
Ian Stirling wrote:
The meters (the cheap ones, the maplin and Lidl 6.99 ones) work out the
current by measuring the voltage/current several times per cycle.
Unfortunately, the lowest cost is got by reducing 'several' as much as
possible.

For things like heaters, or motors, you can almost trivially get a pretty
good reading of power and power-factor (amount current is leading or
lagging voltage) with just 3 or 4 samples per cycle.

This is because the current they draw is a nice sine wave.
Many PC (and other switched-mode PSUs) unfortunately have significant
very fast variations in current.
So, the meter misses these changes, and assumes that the power supply is
drawing a higher current than it should.

So it seems I can't trust the measurements from my device (yet).
Would anyone know where I can learn more about switched-mode PSUs?

Aniseed

Aniseed wrote:

Yesterday I recieved one of the Maplin Power meters in the post. It is made in
Taiwan, by Prodigit Elecronics Co Ltd. Its of reasonlably good quality build,
given the price.

Yes, I've got one now, thanks to all the plugs (sorry) here. I think
it's absolutely fantastic value for money, compared to any professional
instrument (c.f. the price of RS stock no. 292-1274). I've not done any
detailed checks on it yet, but all the readings on stuff around the
house (like yours) seem about right. I've yet to try it though on any
SMPS loads with a high current crest factor and harmonic content though...

One clear limitation is a lack of resolution and the presence of offsets
at the low current end of the range. Mine tends to read 10 mA and 2 W
with no load connected, so the overall accuracy for powers under 10 W is
going to be pretty poor. There's a table of accuracy figures on the
instruction sheet, to which I'd suggest adding plus or minus 2 counts on
the LSD. If I find the time I'll experiment with adding an outboard
10:1 (or even 100:1) current transformer, which should dramatically
improve its performance at low power levels.

I've tried it out on stuff around the house. After much bending over plugging
and unplugging things, I've acquired a list of results and a backache. If
anybody is curious, here is what I found out:

monospace font please
Appliance: Reading:
Kettle rated at 1800-2200W 1980W
Desklamp with 60W bulb 58W
PIII Dell Laptop 20W idle
PentiumPro 200MHz, 1HDD 40W idle
Athlon 1.4GHz, 1HDD 90W idle, 105W runing sims2
Pentium IV 1.8GHz, 2HDDs 75W idle, 100W running hl2
22" Iiyama CRT 5W standby, 70-100W on

All those figures seem quite plausible, IMO[*].

Lower back Light throbbing

Display readability is not its strong point is it? But for £10.63 + VAT
you can't complain!

[*] Below, FYI, is a re-post of some figures I took a while ago and
posted here in Sept '03.

.. Power Current Earth
Equipment /W /A VA PF /uA
-------------------------------- ----- ------- ----- ---- -----
Old sys unit (P75) idle 30 0.185 44.4 0.68 30
Old sys unit (P75) CPU 100% 39 0.233 55.9 0.70 30
Iiyama 17in. CRT monitor 90 0.566 135.8 0.66 60

New sys unit (P4/2.8GHz) idle 100 0.505 121.2 0.83 30
New sys unit (P4/2.8GHz) CPU 100% 155 0.800 192.0 0.81 30
Dell 18 in. TFT monitor 42 0.268 64.3 0.65 40

PSU for computer speakers 4 0.048 11.5 0.35 -

HP LaserJet 4 printer (warm up) 790 3.300 792.0 1.00 140
HP LaserJet 4 printer (standby) 35 0.239 57.4 0.61 140

Notes
-----
Power measurements taken with a Feedback Instruments EW604 wattmeter.
Current figures are true RMS, taken with a Fluke 87.

VA figures are apparent power, calculated assuming Uo = 240 V (i.e. the
approximate actual supply voltage, rather than the nominal 230 V).

'PF' column is power factor (W / VA).

'Earth' column shows protective conductor current (in microamps) taken
on a Fluke 77 (mean responding). Note that the measured figures are far
less than is commonly assumed in threads about spurious RCD trips.

Figures for the monitors were with 'typical screens', not max.
brightness & contrast.

'CPU 100%' figures taken with the SETI at home client running.

--
Andy