In a recent game of Power Grid, someone we play with regularly insisted on a rule that you're not allowed to purchase a "lower" technology power plant than you already have. e.g. if you have 13,17,25 as your power plants, you can't buy 24 or lower if they come up.
He also insisted that if a player didn't win their power plant auction that the market isn't refreshed before they got another chance to bid. e.g. Player A bids cost, player B bids cost + 1 and player A decides not to bid higher. In this scenario player A only gets to choose from the 3 remaining plants next.
The question: are these official rules? I have scanned the rule book and didn't see either, but may have missed them... I also found them quite hard to work with.