How do I replace storage heaters to retain EPC C rating?

Hi, I have a 2-bed flat with 20-year-old storage heaters still in working order. The electrician who reset one recently commented that I should be looking at replacing these shortly and recommended “eco electric rads” and replace the Economy 7 meter (with the cheaper night tariff), with a standard meter. This would require major disruption for the tenants including replastering and redecorating work.

I am concerned that this will reduce my EPC rating from the current C rating to something lower. How can I be sure that these are better from the EPC perspective than storage heaters? The electrician has said that new storage heaters are now prohibitively expensive compared with his suggestion.

I cannot have a heat pump as it’s a third floor flat and the block management would not agree to the external unit. There is no mains gas available to the block. I keep reading conflicting information on what improves and worsens an EPC rating and it seems as clear as mud.

Any suggestions please?

Thanks,

Robert