I was with you until you suggested it would use 5kWh every hour. That's an insane amount of power even if they were using an electric griddle, which is unlikely. A small generator would be enough to power the lighting and refrigeration and then the griddle would run on gas, which is way cheaper than electricity (or the petrol for the electric generator).

I'd imagine energy costs would be a fraction of what you've calculated, and would scale up along with any increase in sales volume.