Brian Gaff wrote on 08/09/2019 :
After all, All the electricity comes from the same generators down the same
wires, so its the admin and of course profit you pay for.

Plus the discounts they get from bulk fuel purchases, from the
suppliers. You would expect that the bigger the energy company, the
more discount they would get, the cheaper they can offer it to their
customers, but the reverse is true. The smaller the company, generally
the cheaper.