Electricity is electricity. Green electricity comes with a certificate which guarantees its origins. Hence it is more expensive than non certificated electricity, if non green electricity goes up in price, the green stuff follows - why? Because the guys selling it get the same as other electricity, plus a bit for the regos (certificates).That's not great analogy but I get that but I don't think you are understanding my point. The supply of electricity provided by renewables hasn't changed and if it had then it will have increased. If the electricity supplier is charging me a premium for the portion of electricity they buy that is generated by solar or wind then they don't have justification for telling my electricty is more expensive because gas and oil have gone up given they are selling me a notion that my electricity is not generated by fossil fuels.
Its not hard.