Which electricity supplier is good for business?

hi im currently with npower electric supplier. for the first year the price is not too bad 9penceper unit. but after 1 year fix term contract they increase up to 18pence. im with them for 2 years now and i think the price is too high its like double from the first year i spoke to them and ask why the price is increase too high and then they said because you not using much electric that why it gone up. my bill is about 100 pounds per quater (9 pence per unit) im using gas heater in winter . i just recieve the letter from them that is my contract is ending in september and the price is still 18p per unit. i would like to terminate the contract and start with another service. which supplier do you think is the best one and i can sign the contract with cheaper price for long term? thank you