Is there not a "demand charge" that is not in your equation. In 1996 the demand charge for 1 MW was $10000 in Ontario. If your normal draw was 10 MWs but you used 15 MWs for 1 hour, there was a $50,000.00 penalty. We used to shed this load by firing up a boiler (and hence electrical production) to prevent a new monthly demand charge. I didn't look at your math because you are pretty thorough with your numbers.