Every house advertised for sale must show a BER, and the seller has to hand over the certificate and the advisory report. Most buyers look at the letter and stop. The letter is the least useful page.
The scale
Since 24 May 2026 new certificates use eight ratings: A0, A, B, C, D, E, F and G. A0 is the top and is only for homes that are very efficient and burn no fossil fuel, so a house with a gas boiler cannot get it. The sub-grades (A1 to A3, B1 to B3 and so on) are gone. A certificate stays valid for ten years, though, so most houses on the market still carry the old fifteen-band scale. Check the issue date before you compare two houses.
The number under the letter, kWh per square metre per year, is what the rating summarises. The CSO, which converts old ratings to the new letters for its statistics, says the energy thresholds are identical for C and above on both scales. So an old B2 is a B today and an old C3 is a C. A 1970s semi with no insulation upgrade is typically D or E.
The advisory report
This is the assessor’s list of what they saw and what each upgrade would do. Walls, roof, floor, windows, heating, ventilation, each with a current and a potential rating. It tells you whether an F is an F because of a single 1990 boiler or because the house is solid-wall with single glazing. The first is a €4,000 fix. The second is a deep retrofit. Same letter, very different purchase.
Money
Green mortgage rates depend on the BER, and each lender sets its own band. AIB, for example, asks for A1 to B3 on an older certificate, or A0, A or B on one dated after 24 May 2026. Ask your lender for its band, then look at the advisory report: a house one attic job away from that band is a real saving over the term. At the other end, SEAI grants cover part of a retrofit; a One Stop Shop deep retrofit on a typical semi runs from €25,000 upwards after grants. Price that in. A seller cannot argue with their own advisory report.
Checking
The SEAI register lets you look up a certificate by its number. The report on this site pulls the certificate and the advisory report for the Eircode, translates the rating to the 2026 scale and attaches both PDFs, so you have them before the viewing rather than after the offer. By area: BER ratings by county and town.