You will be billed every quarter for all the gas and electricity 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 area of your premises and the nature of the machinery and equipment you will be using. (You may need to install a three phase electricity supply.) You can adjust the figures once you have been in the premises for a few months to make your financial forecast more accurate.
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.
Climate Change Levy
UK businesses are now liable for the Climate Change Levy (CCL), an energy tax that can add around 15% to typical energy bills. Intensive energy users can join the CCL Discount Scheme which reduces the tax payable provided certain targets are met. The Food Storage and Distribution Federation (FSDF) has negotiated a Climate Change Levy Agreement for the food and drink industry and it would be worth contacting them to find out if you can benefit from joining the scheme. Details of the scheme are available on the FSDF website.