Well, some data would be advisable. Is it a loss leader? Is their ice cream priced lower than wendy's, burger king, in-n-out or similar? To the best of my knowledge, none of those places have this problem.
If the cone is profitable to sell, then it's not a loss leader and they have every incentive to sell as many of them as they can.
Two of those three are not really marginal costs. Yes, it costs electricity to make the food, but _stable_ electricity is something you already need in the biz, same as rent. If you need a generator, you already have one.
Also, enlighten me: are markets where electricity grids are unstable the same ones where retail space is expensive?