You will be billed every quarter for all electricity and any gas you have used in the business. This could be energy supplied to your business premises or extra energy used at your home, depending on where your business is based.
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 any equipment you will be using (for example, cooking range, fridges and so on). You can adjust the figures once you have been in the premises for a few months.
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.