So your answer is that you leave your PC on 24/7/365 because it doesn't cost much extra, but it does not matter either way because if you didn't use more electricity, costs would go up for everyone on your "block?" If so, then wherever you are, there is a negative feedback loop of using less costs more so you mind as well use however much you can afford because its saving you money in the long run.
LOL. Not really. My pc is SFF mITX with a full custom loop. There's zero room to do anything inside. It's a 'set it and forget it' pc. That said, it's also an Asus mobo and there's an issue where if I change anything manually in bios, my nvme disappears at shutdown and requires a hard reset of cmos to clear the bios and may have to do that 3-4x before the bios magically finds the boot nvme again. So since Asus said it was an nvme issue, they won't RMA the mobo, the nvme is not proprietary, it uses standard drivers, so that can't be RMA either because they said it was a mobo/bios issue. So my fix is to simply not go through shutdown procedure, funny but power outages don't affect the drive, starts right back up no issues.
But I also ran my old pc 24/7 because it was generally faster and easier to Google stuff on it than use my phone, same with the wife, and it's considerably easier to read a bigger screen at our age, so it was a convenience thing.
But yes, when local grid use goes down, the power companies raise the price per watt a little or end up not making enough profit to do things like maintenance, repairs, rebuilds, expansion, pensions etc after what they need to dish out to buy the block of units from the actual power plant. The plant doesn't sell individual watts, it sells blocks, maybe a 1Mw block of power, if the power company needs 1.1Mw, it has to buy 2 blocks, 2Mw, to get that rate, if the power plant agrees to just selling a half block, 500kw, it costs more than half of a 1Mw block, as much as 3/4 the price. So any minor deviation, whether higher or lower, doesn't change anything, the power is already bought from the plant in expectation of what the average use will be from the grid, plus some spare for emergency use etc.
It's also why power companies are not interested in partial solar, that cuts into their profit hard, but are very interested in full solar because they'll pay you 5¢ per kw, instead of paying the power plant 10¢ per kw in a big block, so if they get enough ppl to go full solar, that 1.1Mw, they'll pay cheap for the 0.1Mw, and only buy a single 1Mw from the plant, not change the prices, and make profit over double what they pay the solar ppl. It's a win-win all around. That's why power companies will also help you go full solar, even pay for it fully, because it makes them money.