Its most likely the same problem as internal power sources should generator power reserves especially if you choose store as your not selling any unused power or water to the utility company. Ok say like you have a mothly bill of 232 dollars in real and you store power on a disconnected generator, that uses gas. The power company can't tell you that you can't hook up your house to a power generator. Your get power that is not counted by the company because its internal to the lot. I expect it to work the same way in the Sims 4. You generate power on lot and set everything in the bills section to store, when 24 hours after bills arrive they shutoff your power, and water even if the water and power generators are running.
