# when my battery back displays the watts...

Discussion in 'Community Discussion' started by vaderhater245, Apr 21, 2009.

1. ### vaderhater245 macrumors 6502

Joined:
Mar 4, 2008
Location:
Flagstaff, AZ
#1
I'm pretty sure this is a dumb question but I'm asking it anyway. I purchased an APC Battery Backup for my computers and its displaying the average load as 200w. This is with a Custom Built PC running idle, a 06 MBP on and idle, a 08 macbook idle, and a Samsung T260HD connected to the PC. Is this 200w continuous or per hour? It doesnt make sense to me. Does it mean im using just as much power as 3 1/2 60w light bulbs?

2. ### mkrishnan Moderator emeritus

Joined:
Jan 9, 2004
Location:
Grand Rapids, MI, USA
#2
A watt is a unit of power consumption, not energy. This is why your electricity bill measures consumption in something like Watt-hours instead of in watts, right? So the wattage gives you the rate of consumption, not the consumption.

Now the average load measures the rate of energy consumption over time smoothing out, essentially, the peaks and troughs.

So yes, what it's saying is essentially as you said, if I understand correctly, that your computers and monitor on idle consume about as much energy as the 3.5 light bulbs.

My guess is that it would break down something like...

Macbook and MBP on idle = 15-20W each
Monitor = about 60-80W
PC = about 100-120W.

Which is roughly how you come to your 200W.

If you put all of them to sleep, the number should drop down significantly, to something like 3-4 watts per device, or maybe <20 watts total.

3. ### chrmjenkins macrumors 603

Joined:
Oct 29, 2007
Location:
CA
#3
When we talk about power, we usually refer to it in Watt-hours, which is actually a measure of energy (joules). When it says 200W, it's telling you the instantaneous power (which is sort of redundant, because power is instantaneous, but I'm using to distinguish). So, if they continued on that average for an hour, they'd use 200 Watt-hours, which is how you're billed.

Basically, take your overall average watt draw, multiply it by the hours in your billing period, and voila, there you go.

edit: Oh bugger

4. ### Rodimus Prime macrumors G4

Joined:
Oct 9, 2006
#4
You computer is consuming 200 watts continuous.

You power company is going to bill that usage at 0.2 Kwh which works out to be about 20-30 cents a day to run. If that helps out at all.

5. ### miles01110 macrumors Core

Joined:
Jul 24, 2006
Location:
The Ivory Tower (I'm not coming down)
#5
The Watt-hour is a stupid unit. Why measure in Joule-hours per second? Agh.

6. ### mkrishnan Moderator emeritus

Joined:
Jan 9, 2004
Location:
Grand Rapids, MI, USA
#6
Yes, of course it is, in terms of elegance. On the other hand, it's pretty practical -- it works pretty well actually in discussing real world usage of a device. It's much easier to estimate how many hours a device is being used than how many seconds, and it obviates the need for multiplying things by 3600....