This is supposed to be an old-school operation, right? The coal-fired generating plant that Hawaiian Electric Co. depends on is a conventional facility that should supply power reliably.

But it didn’t, of course, resulting in outages two days in a row, inconveniencing thousands. Coal and other fossil fuels — anything that is simply burned to make electricity, including biomass and H-POWER trash — is valued as “firm power,” energy you can count on. The variable sources such as wind or so- lar are considered less constant.

Bet the residents who have solar photovoltaic cells on their rooftops are feeling pretty firm about the payoffs of that investment.