I don’t get why that would be a nightmare. In my country the electricity prices change per hour for dynamic contracts (they just follow the energy market) and with normal usage it’s cheaper on average than fixed contracts, including those with peak and off-peak rates. For gas it’s a day price, again same as the energy market. For both electricity and gas the prices for the next calendar day are published in the afternoon (that’s how the energy market works). The companies charge a little extra per unit and a small fixed fee per month.

Contracts with fixed rates (including nighttime and daytime rates) have to buy in advance, which means that unforeseen circumstances are included in the price and they also have to account for the fact that they might need to buy extra or sell off their excess based an actual usage.