Is that summer peak period pattern true for the Great Lakes region too, or is it true for the whole of the USA?

17,513 MW divided by 0.016 mWh (10,656 kWh per household annually) and there are 3.8 millions households in Michigan.

I can't see how your calculation works out. 10,656 kWh of electricity consumed annually would be 0.0012 MWh consumed hourly (i.e. an average power need of 0.0012 MW), not 0.016 MWh. You also seem to have forgot the capacity factor. Here is one way how it could be calculated correctly:

Taking 25% for capacity factor, those 17,513 MW would produce 17,513 MW x 24 hours x 365 days x 0.25 =  38.35 TWh annually, while households would need 10,656 kWh x 3,600,000 = 38.36 TWh annually. By pure accident, that covers demand exactly!

_{*Lunatic*, n.
One whose delusions are out of fashion.}