You are right. I was just going off the source I found, which accounted for some of the aspects you point out, but not all. These numbers simply provide a rough estimate, and detail how the sys admin certainly did cost the school district real (and potentially very substantial) sums of money.
> Even more complicated is the heat.
You make a good case for the winter months, but the opposite would hold true for the summer months when the heat becomes a real issue and additional air conditioning may be necessary, etc...
> Edit: also if it was a public school, wouldn't they be off for about 3 months over summer ?
Not necessarily. Usually over the summer months (for a traditional schedule school as opposed to a year-round schedule like many public schools are these days) some of the staff is typically on campus monday-friday doing various administrative tasks, workshops, prepping for the next school session, moving classroom furniture, cleaning, etc... IT staff would be included in this, and therefore we can reasonably assume the sys admin was still running his systems.
Yes, it will draw even more than 350 Watts at full load. 350 is the output power, whereas incandescent lightbulbs are measured in input power. So a 350 watt power supply, depending on efficiency of the PSU anyway, is probably using around 400-500 Watts at the wall at full load.
And that's a pretty awful efficiency you suggest. It may be that bad, but I'd sure hope not.
Talking about power load, though, I have a Kill-A-Watt pass-through power meter, and I have measured power at the wall exceeding the rated output power capacity of an 80% efficient power supply on a computer running at full load (running a graphically and computationally expensive computer game).
A lot of PSUs are pretty inefficient. You can look up the stats. It wasn't until recently that you even had a lot of them earning the 80 Plus "bronze" rating, which is 80% efficiency. There's still plenty with worse efficiency than that. A decade ago, you're probably looking at 60% efficiency on average.
What grandparent commenter showed was the school district's numbers are plausible. I doubt the district entered into a legal battle without first consulting an engineer or two about the electric costs.
HP 6000 Pro SFF - Core2Duo E8400 @ 3GHz - 100% CPU: 70, Idle: 26, Sleep: 2-3, Off: 0-1,
HP 6200 Pro SFF - Core i5 3470 @ 3.2GHz - 100% CPU: 83, Idle: 31, Sleep: 2-3, Off: 0-1,
HP 6300 Pro SFF - Core i5 2400 @ 3.1GHz - 100% CPU: 100, Idle: 30, Sleep: 2-3, Off: 0-1,
It's been a few months now, and I can't remember what I used to max out the CPU. It wasn't SETI @ Home, but it should give you a pretty good approximation. When it was off, it had Wake on LAN enabled, so it still drew some power. But it would fluctuate between 0 and 1.
They may be off for 3 months over the summer. Which might mean they were actually off, or it might mean that they ran 24/7 and NONE of that time was for 'educational' purposes.
PSU's arent light bulbs. A "350 watt" psu doens't draw 350 watts. That's the theoretical maximum you can draw from it. Sure, SETI was probably drawing a higher load than idle, vs off, but I highly doubt it was drawing 100%.
Even more complicated is the heat. If they lived in a cool climate, at least some of the waste heat that was emitted would have been absorbed by the building, which they are (presumably) paying to heat at least a few months of the year.
Edit: also if it was a public school, wouldn't they be off for about 3 months over summer ?