You will be billed every quarter for all the electricity and any gas you have used in the business.
Until you have been trading for a few months you will not know exactly how much energy the business will use. Your energy supplier may be able to give you some guidance, based on the size of your premises and the nature of the equipment you will be using, such as freezers. You can adjust the figures once you have been in the premises for a few months.
Energy prices are high and seem likely to keep on rising in future, so it makes good sense to include efficiency measures in your design if you're refurbishing your ice cream parlour or designing the premises from scratch. Even small measures, like fitting low-energy lighting, can have a significant benefit over time.
It's worth shopping around the different energy companies to get the best deal for your business, particularly if you're going to be a heavy energy user.