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. You can adjust the figures once you have been in the premises for a few months.
Because of the nature and value of the items you're likely to be working on, you may need to be able to ensure that you can control the temperature and humidity within a certain part of your premises.
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.