Actually, I will mention that here in Ontario, larger organizations get their electricity on HOEP pricing (https://www.ieso.ca/imoweb/marketdata/hoep.asp). HOEP basically stays at a fixed market rate, provided that electricity demand is close to projected electricity demand. When demand differs from projections, the price fluctuates. You can get the current price off their website, updated in realtime.
If demand is too high, the price goes up, and if demand is lower than expected, the price goes down (because they have extra capacity, possibly from nuclear sources that can't easily be spun down, that they need to bleed off somewhere.) Sometimes, the price actually goes substantially negative, but usually only for a few hours a few times a year.
So, if you're on your local supplier's equivalent of HOEP, you might review your historical pricing, and see if it's worth your time an effort to build a system that starts furiously mining when the price goes low/negative.