A lot of landlords write off ECO4 the moment they realise their tenant doesn't claim a qualifying benefit like Universal Credit or Pension Credit. That's only half the picture. Every principal area in England and Wales can, in principle, run its own "flexible eligibility" route into ECO4 alongside the national benefits route — a route usually shortened to LA Flex.
We haven't independently confirmed that Merthyr Tydfil operates a live LA Flex Statement of Intent for landlord referrals — councils publish, update, and occasionally quietly pause these documents, and there's no central register. Before assuming a Merthyr Tydfil rental is ineligible on the benefits route alone, check with the council directly (search "Merthyr Tydfil ECO4 Statement of Intent") — the alternative route is worth £5,000–£15,000 of grant value on a single qualifying measure, so a phone call is well-spent time.
Merthyr Tydfil is a Welsh principal area, so it handles retrofit-grant delivery end-to-end — no separate district layer. ECO4 rules run across England, Scotland, and Wales, so Welsh landlords with rentals in Merthyr Tydfil sit on the same national scheme as landlords in England, with LA Flex working through the principal area rather than through a district council.