At that scale, they may be doing more interesting things, like participating in whatever passes for a spot market, or even time-of-day arbitrage. There is cons

At that scale, they may be doing more interesting things, like participating in whatever passes for a spot market, or even time-of-day arbitrage. There is considerable variation region-to-region, but a common pattern is for the spot market to clear every 15 minutes to provide secondary frequency reserve, with a day-ahead market that clears 24 hours in advance, and a wide range of futures markets that build on the day-ahead market.