My findings about power consumption by various gadgets

[vasishta.sushant]

I just bought this electronic clampmeter, primarily to test how much power each component at my home is consuming. Since I am little too finicky about my monthly power bills, wanted to optimize my usage based on the power usage.

Basically I simply noted the voltage and ampere ratings at the AC main, for the various appliances/combination of appliances. Kindly do note that the meter I bought might not be dead perfect with its findings but nonetheless it gave a good picture of the power consumption pattern at my home.

I tested the following things primarily:
1) LG 32" HDTV
2) My PC (Phenom II 925, 4GB RAM, ATI 5770, APC 550VA UPS and other sundry hardware)
3) PS3 500GB (latest 25xxx version)
4) Onkyo 3300 HT System
5) Airtel IPTV Settop box

I'll simply put my findings (only Amp rating. Multiply with 220 to get the actual wattage), as I noted them:

PC+TV+AVR
=========
Idle PC Usage : 1.1
Music Playback on foobar (low to medium volume/high volume): 1.2/1.5
Movies: 1.2 (little strange. I was hoping more)
Gaming(Cutscenes/Main): 1.5/1.9


PS3+TV+AVR
==========
Music: 1.1
Gaming (didnt check)


PS3+AVR (with TV turned off)
======================
Music: 0.6


Only AVR
========
(Music with netbook running on battery): 0.2


Only TV (with IPTV Settop box)
========================
0.5



Some strange observations:
=====================
* Turning off all the channels other the main fronts does not have any effect on the power consumption of the HT system. Earlier I used to turn off the center/sub/rears, thinking that it will save some energy, while listening to the music. I guess the AVR takes care of this automatically.

* UPS itself is extracting like 0.1. This is strange since this equates to nearly 22W power consumption, even when nothing is connected to the UPS (in my case the PC and PS3 are connected to the UPS and the rating was noted when both were on standby/turned off mode).


This was it.

Helped me a lot since I can listen to the music now without the worries of hefty power bills at the month end. My AVR is rated at 350W which made me use it as less as possible (miser me ). At least now I do not have that tension on my mind.


If you guys want me to check any other parameters as well, let me know.

 

[NetFreak]

I'll simply put my findings (only Amp rating. Multiply with 220 to get the actual wattage)

You will have to consider power factor to calculate wattage. Reason is, equipment like AVR/PC have rectifier circuits that distort PF.

And if some inductive load like Compressor in fridge kicks in (while you are measuring amperage), it can tilt this further.

PF can be discounted if most equipments are 4 stars or more for energy consumption. Its a requirement to have PF > .9 to achieve 4 stars.

 

[vasishta.sushant]

Dude, I guess you are not getting it. I am measuring the usage at the AC outlet. Why would you need the power factor in that case ?

 

[NetFreak]

Because with AC:

Wattage != Voltage * Amperage

If you are drawing 10 Amp @ 220V, wattage would not be 2200. It could be 1800 to 2000 depending on PF (Average PF is .8 to .9 for Indian homes).

And it would vary from appliance to appliance. E.g. a simple heater has PF of ~1.

 

[kapvin]

You will have to consider power factor to calculate wattage. Reason is, equipment like AVR/PC have rectifier circuits that distort PF.

And if some inductive load like Compressor in fridge kicks in (while you are measuring amperage), it can tilt this further.

PF can be discounted if most equipments are 4 stars or more for energy consumption. Its a requirement to have PF > .9 to achieve 4 stars.

thanks for the info. didn't know that the star rating of the BEE included a power factor spec too. way to go.. BEE.

nefreak.. do those "kill a watt" devices available online have any method of capturing power factor?

 

[vasishta.sushant]

Because with AC:

Wattage != Voltage * Amperage

If you are drawing 10 Amp @ 220V, wattage would not be 2200. It could be 1800 to 2000 depending on PF (Average PF is .8 to .9 for Indian homes).

And it would vary from appliance to appliance. E.g. a simple heater has PF of ~1.

My friend, i am glad that you know the term POWER FACTOR but i feel a little sad when I see that you don't know what it means and how to implement the theory.

PF tells how efficient a device is. A PFof 0.9 means that the device is capable of utilizing 90% of power fed to it. What does this imply ? A 1000W device would actually consume 1000/0.9=1111W to generate 1000W of output.

Which in turn means, to run a 1000W device, we need to pay the power bill corresponding to 1111W of power consumption.
What you are saying is converse of it. A low efficiency device will consume more than its rating and a higher rating device would consume closer to what it states. Only a 100% efficient device, i.e. with PF=1, will consume the rated power.

Now my idea here is not to see what is the rated power of my devices (I already know them), I wanted to measure how much they are consuming. Since I am measuring directly at the wall outlet, the PF thing would simply not come into picture.

It'd, however, come into play if I try to find the power output by seeing the device specifications.

Getting the drift ?

 

[NetFreak]

nefreak.. do those "kill a watt" devices available online have any method of capturing power factor?

Not sure about that..

PF tells how efficient a device is. A PFof 0.9 means that the device is capable of utilizing 90% of power fed to it. What does this imply ? A 1000W device would actually consume 1000/0.9=1111W to generate 1000W of output.

This is wrong. You are confusing efficiency and PF.

For example a DC device would never be 100% efficient, but it would still have perfect PF (1). E.g. :

To do work worth 90W, DC device would consume 100W and 10W would be consumed due to inefficiency (converted to heat etc).

But it would still draw 10 Amp on 10V to consume 100W.

But an AC device might draw 11 Amp or more to consume 100W at 10V.

Thats why unless PF is known wattage can not be calculate for AC devices.

 

[gobble]

Nice Ping-Pong match!! hyeah: My head is turning left and right and left from Netfreak to Sushanth and back ... in sync with the chops and smashes

I hope the ball doesn't hit me in the eye ...

Cheers

 

[arj]

Netfreak is right. PF is a parameter for input power itself, it is not component related ! typical indian power input is standardized at .8 hence VA must be multiplied by this factor ( thats why any invertor is shown in VA and the power rating is usually 80% of it)

In reality this fluctuates lower and is never at .8 while industrial units are on.

 

[anm]

it is a vector product of current and voltage and not scalar product. Angle between current and voltage is what determines the PF, IIRC.

 

[moktan]

power factor of an ac circuit is defined as the ratio Power Absorbed/IV, since IV is the maximum power that would be absorbed if the whole circuit was a resistance, in which case the power would be dissipated as heat as in a heater...
pure inductors and capacitors absorb no power over a complete cycle of an ac..

 

[Rockfella]

Nice thread Sushant ... but most of it went over my head

 

[cmsajith]

I think the OP is trying to find how much current is being consumed when he is using a device, let it be a heater or a fan or an amplifier. He is not concerned about the consumption of that particular device and the wastage as heat. So no need to consider the PF as this is required only to find out how much energy is wasted.

Power factor - Wikipedia, the free encyclopedia

PF is valid if we try to calculate the consumption in the reverse way. eg, a device rated as 200w in the specs (called Apparent Power). To find the RealPower, we need to consider the PF of that device.

Kill-A-Watt is a similar device but it does the calculations internally and shows the power consumption. Moreover it cannot detect which device is connected to it. It just finds the power consumption (I would rather say power demand at the socket). It also can store the history. But 230v version is not available.

 

[anm]

Anyways, OP has done a good job in finding out a rough comparison of how each device is fairing.

 

[borg]

I think the OP is trying to find how much current is being consumed when he is using a device,

[I]You mean how much current is "drawn" by the device?[/I]
PF is valid if we try to calculate the consumption in the reverse way. eg, a device rated as 200w in the specs (called Apparent Power). To find the RealPower, we need to consider the PF of that device.

Normally AC devices are rated in VA and we need p.f to find the W.if already the spec is in W that means the p.f is unity[/I]

.

If the point of interest is the power consumption of AC operated devices then p.f is verymuch required,. example, suppose the device draws 10A@230V, then by OP's method we assume it consumes 2300W, when its p.f is 0.1 and and actual consumption is only 230W. In case of highly reactive loads like transformers above scenario is very much possible

without a true rms responding powermeter it is very difficult to accurately measure/compare the consumption of these

 

[NetFreak]

I think the OP is trying to find how much current is being consumed when he is using a device

Precisely this measurement will tell us amount of current being consumed at that point in time.

However, we are billed for wattage (1 Unit = 1 kWh) and not for current.

To look at wattage we need either a KWH meter or need to know approx PF of device.

 

[Thad E Ginathom]

Or... turn everything else off and check the meter reading over an hour or so?

If this is not possible, because the current drawn is too small, then (ok, yes, it all adds up) I can't imagine why anybody would be bothered about it!