[ps2cho]

I have a Kill-A-Watt monitor which reports my HTPC to be about 99W idle.


Now, I have a Corsair 450VX which states 85% efficiency.


Does that mean that, I am actually 85% OF 99W for the "THEORETICAL" wattage of the system? OR does that mean 99W is 85%, so Realistically being 116W? Which way round is it?


Next, Let's say I run this computer 12hrs a day, 7 days a week idle for the most part, how can I figure out running costs? How is kWhr figured out?


Trying to figure out if its worth swapping my 65W X2 3600+ for a BE-2350 45W for $37.

 

[walford]

Changing your power supply won't change the amount of power your PC consumes unless the new power supply is a "green supply " that wastes very little power.

Think if it like the amount of warter you house uses does not depend on the size of the pipe coming to the house.

 

[Ben_Tech]



Quote:
Originally Posted by ps2cho /forum/post/15397573


Does that mean that, I am actually 85% OF 99W for the "THEORETICAL" wattage of the system?

Yes. But, the efficiency factor of power supplies typically tapers off below their optimum range which is usually around 200 watts. I would estimate 75-80% at best.


And no, changing the processor is not worth it, use cool n' quiet or CrystalCPUID (guide) http://www.silentpcreview.com/article231-page1.html to regulate the voltage settings of your current chip.

 

[Ben_Tech]

Oh, and using that button on the right side of your Kill-A-Watt along with the following web calculator you can make the most of the thing.

http://www.odograph.com/experiments/php/kilowatt.php

 

[nm88]



Quote:
Originally Posted by ps2cho /forum/post/15397573


Next, Let's say I run this computer 12hrs a day, 7 days a week idle for the most part, how can I figure out running costs? How is kWhr figured out?

1 KWh = 1000W consumed for 1 hour.


So take your typical power consumption in watts from the wall outlet (this is TOTAL consumption, plus your power supply's inefficiency), divide by 1000 to get Kw, and multiply by 24 for one day, or 732 for one month.


Now multiply by your top marginal rate on your electric bill to find out how much it costs.


There's also a feature on the Kill-A-Watt that can add up KWh over a period of time, but this is unnecessary. Just take your idle power reading and use that.

 

[Bigbird999]

Your load from the wall is 99W (call it 100 W = 0.1 KW). That is what your PC is consuming.


How the pc uses the power is dependent on your hardware. The first thing is that the psu takes the 100 w of AC power fom the wall and converts it to DC power for all of the devices in your pc. In your case, the psu does this conversion at 85% efficiency so it produces 85 watts of DC power and 15 watts of heat (warm air from your psu fan).


Currently, the power consumption of your rig is 0.1 x 24 = 2.4 KWH per day. Depending on where you live, power costs are 5 - 20 cents per KWH (lets say 12 cents) so it will cost you between 12 x 2.4 = 29 cents per day or about $9 per month to run it 24/7. If you put in a lower power consuming cpu, then the 99w will drop by some amount, but how much? The most that the power requirement of the hardware could drop would be 20 W (65 vs 45 w cpu). So the requirement from the wall (allowing for the 85% efficient psu) would be 20/85% = 23 W less or ~ 75 W or ~ 1.8 KWH per day =1.8 x 12 = 22 cents per day = $6.50 per month So a saving of about $2.50 per month.


Or you could just assume a 20 W load reduction and calculate a savings of 20 x 24 / 1000 = .48 KWH per day = 6 cents per day x 30 days = $1.80 per month. Not a lot but every kwh counts.


BB

 

[ps2cho]



Quote:
Originally Posted by Bigbird999 /forum/post/15398999


Your load from the wall is 99W (call it 100 W = 0.1 KW). That is what your PC is consuming.


How the pc uses the power is dependent on your hardware. The first thing is that the psu takes the 100 w of AC power fom the wall and converts it to DC power for all of the devices in your pc. In your case, the psu does this conversion at 85% efficiency so it produces 85 watts of DC power and 15 watts of heat (warm air from your psu fan).


Currently, the power consumption of your rig is 0.1 x 24 = 2.4 KWH per day. Depending on where you live, power costs are 5 - 20 cents per KWH (lets say 12 cents) so it will cost you between 12 x 2.4 = 29 cents per day or about $9 per month to run it 24/7. If you put in a lower power consuming cpu, then the 99w will drop by some amount, but how much? The most that the power requirement of the hardware could drop would be 20 W (65 vs 45 w cpu). So the requirement from the wall (allowing for the 85% efficient psu) would be 20/85% = 23 W less or ~ 75 W or ~ 1.8 KWH per day =1.8 x 12 = 22 cents per day = $6.50 per month So a saving of about $2.50 per month.


Or you could just assume a 20 W load reduction and calculate a savings of 20 x 24 / 1000 = .48 KWH per day = 6 cents per day x 30 days = $1.80 per month. Not a lot but every kwh counts.


BB

Oh okay so it still produces the wattage that the whole computer produces, it is just that the extra comes from the heat produced by the PSU....

 

[Bigbird999]

The whole PC (PSU, mobo video card, hard rive etc) is using 100W. That is what you are paying for. Each component of the PC uses some of the 100 watts to do its work. The PSU is using 15 W of the 100 W total to do its work. The CPU is using up to 65 W to do its work. the HDD is using ~ 5 W to do its work, etc. If you change the CPU to a lower wattage unit, it will use less power so the total load will be reduced.


BB