A landlord heating override DESCRIBES the dwelling, so its assumed off-peak meter
(Dual/E7) is a coherent default — it must not downgrade a cert that already
lodges a more-off-peak meter (e.g. property 709874's 24-hour all-low tariff). The
overlay opts in via keep_existing_off_peak_meter; _fold_heating then keeps the
cert's meter when both it and the desired meter are off-peak. Heating MEASURES
build HeatingOverlay directly and leave the flag False, so they still re-meter
for real (Elmhurst re-lodges 18-hour -> Dual on a storage install) — the cascade
pins stay green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>