We have just renegotiated the electricity contract on an office building we manage. If the usage is high enough, we can approach competing suppliers to quote to supply power and contract fixed pricing for 1, 2 or 3 years. The charges for supply, only amount to around 40% of the bill - the balance is made up of service charges (poles and wires), environmental levies  etc. This time around, prices were higher. The surprising thing was the difference in quotes between suppliers. The chosen supplier was considerably less than the company that had the contract. The lesson is, if you just renew with your current supplier without getting other quotes, it can be very expensive! The other interesting thing about the quotes was they all showed lower prices for years 2 and 3, compared with year 1. It really pays to do your homework.