EPC deltas as a product input.
The current rating is disclosure. The gap between current and potential is a product - the retrofit headroom a green tranche is designed around.
Current and potential EPC ratings are published together, so the retrofit delta - the gap between where a property is and where it could reach - becomes a product input rather than a disclosure line.
The current EPC rating tells you where a property is. On its own it is a disclosure line - useful for reporting, inert for product design. The number that designs a product is the second one: where the property could get to.
The delta is the input
We publish current and potential ratings together, from the register where a certificate exists and modelled and clearly flagged where it does not. The gap between them - the retrofit delta - is the field a green proposition is actually built on.
IF potential_energy_rating >= "C" AND current_energy_rating < "C" -> eligible for green trancheThe current rating is disclosure. The delta between current and potential is the product.
Where the delta earns its keep
- -Retrofit-incentive design - the properties with the most headroom are where an incentive changes behaviour.
- -Green-tranche eligibility - a defensible, property-level rule rather than a postcode proxy.
- -Transition-risk and disclosure reporting - improvement potential across the book, not just current state.
Running cost is a property fact
Alongside the ratings sits an estimated monthly running cost. It belongs to the property, not the person. It is affordability context on the building - what it costs to run - and it is never a signal about the borrower. Keep it firmly on the property side of any affordability picture, and it is a genuinely useful input; drift it toward profiling the applicant and it is neither useful nor allowed.
Honesty about coverage
Where a certificate exists, the rating is register-based. Where none does, the value is modelled and flagged so a rule always knows which it is acting on. Coverage is stated per nation - stronger in Great Britain, partial where the register is thinner - rather than assumed. A green product built on a silently modelled rating is a product built on sand; a flagged one is a product you can defend.