Wouldn't this model price out poor people? Doesn't that mean the most vulnerable people cant afford the services when they need them most, ie max hot/cold?

Changing the utility to a market sort of defeats the point of trying to optimize the utility.

A typical user still pays the same on average in a market.

Just they might pay more in some hours and less in others.

Some market systems have gotten bad press over huge bills (eg. Texas), but that only happens when only a small chunk of users participate in the market, whilst others are on fixed pricing and therefore don't care about usage.

When everyone participates, supply and demand make sure the price never goes super high, simply because there are enough people who will turn off stuff to save money.