Appropriate proof that the extension was completed before the day of accomplished installation consists of: For newer measures installed on or soon after 1 January 2020, all electrical storage heater repair service, alternative or enhance should be accompanied that has a two-12 months guarantee. This can be a company’s guarantee. https://freeecogrants.co.uk/why-should-you-apply-for-eco-funding-first-time-central-heating/