Power consumption

Editor's note: you do not want to bother yourself by reading this blog post. 
So. These dang MacPro towers run very hot. Also, my studio now has a deal where I pay my own electric costs. As a classic model in economics, this now encourages me to reduce the amount of electricity I use.
Note that the amount of heat is directly related to the amount of electricity.
When asking about the charges per kilowatt hour, my landlord gave me this handy chart:

this month it's $0.34

in june it was $0.31

in april $0.27

Of course it's not consistent. That would make calculations too easy.
I feel fairly confident Mac Pro eats between 115 and 318 watts. is about 85kW/h to 235kW/h a month. And if we pretend that we pay thirty cents a kWh, that's somewhere between $25 and $75 a month. Probably not quite $50 on average. I'd guess about $30 on average.
Still, that's $360 a year.

Our office is number 10.

Thing is, nowadays, I could get a Mac Mini for a thousand dollars which benchmarks faster. Those are between 11 and 85 Watts. So maybe 20kWh a month? So electric cost of six bucks.
So it'll cost about $72 a year to run a new mini. Versus $360 to continue to run the old Mac Pro.
The new mini would pay for itself in about 3 years. And it would irritate us with its heat consumption vastly less. And the fact that the mini is faster means it won't even be working as hard as the Pro.
Huh.