That could mean anything from about 5 kW upwards, which I believe is around $3500/year of electricity in Calgary. Can you be a bit more specific?

Not really. It's not my department. dsr wanted a clue, that's the best one I've got...

Here's something from 2006 that quotes Theo saying the bill was around 100 USD/week.

http://openbsd.das.ufsc.br/press.html

and something else that says $600/mo:

https://forums.freebsd.org/viewtopic.php?t=38488&p=218116