Chapter 9 of 10 · Self-build, extending and renovating · 1 of 8
BER ratings explained: what A to G means, what it costs to heat, and how it affects your mortgage
Checked 21 Oct 2026the Central Bank's mortgage measures, Revenue's rules and the scheme operators' published terms.
The BER scale from A1 to G, what each band costs to heat, how ratings affect mortgages and value, and how to read the advisory report.
Check before you hire: a ber assessor should be on the register kept by SEAI. SEAI: register of BER assessors
Written in plain English for the person buying, selling or switching. This guide covers the Republic of Ireland only.
A Building Energy Rating, or BER, is a label for how much energy a home needs to heat, light and ventilate. It runs from A1, the best, to G, the worst, like the label on a fridge. Every home for sale or rent must have one. This guide explains the scale, what each band means for your bills, how lenders use it, and how to read the report that comes with it.
What a BER measures
A BER assessor (on SEAI's register; see the BER assessor page) visits the home and measures the walls, windows, roof and floors. The assessor records the insulation, the heating system, the hot water, the lighting and any solar panels, and feeds it all into SEAI's calculation. The result is a figure in kilowatt hours of energy per square metre of floor per year, written kWh/m²/yr, and a band on the scale.
It is a measure of the building, not of the people in it. Two identical houses have the same BER whether one family keeps the heating on all day and the other never turns it on. It does not measure your bills; it measures what the home would need under standard conditions.
The scale
| Band | Energy per square metre per year | What it usually is |
|---|---|---|
| A1 | 25 kWh or less | A new home with a heat pump and solar panels |
| A2 | 26 to 50 | A new home built to current regulations |
| A3 | 51 to 75 | A new home, or a deep retrofit |
| B1 | 76 to 100 | A well insulated home with a modern heating system |
| B2 | 101 to 125 | A home built in the 2010s, or a good retrofit |
| B3 | 126 to 150 | The threshold for most green mortgage rates |
| C1 | 151 to 175 | A 2000s home with some upgrades |
| C2 | 176 to 200 | A typical 1990s or 2000s home |
| C3 | 201 to 225 | A 1980s or 1990s home with attic insulation |
| D1 | 226 to 260 | An older home with partial insulation |
| D2 | 261 to 300 | An older home, single glazed or an old boiler |
| E1 | 301 to 340 | A 1960s or 1970s home with little insulation |
| E2 | 341 to 380 | The same, with an older heating system |
| F | 381 to 450 | An old home with no insulation |
| G | Over 450 | An old home with no insulation and open fires or electric heaters |
The bands are SEAI's. A G home needs more than eighteen times the energy of an A1 home for the same floor area.
A worked example of what it costs
Take a 100 square metre house. At the top of band C3 it needs 225 kWh per square metre, so 22,500 kWh a year. The same house at the top of band B2 needs 125, so 12,500 kWh. The difference is 10,000 kWh a year.
What that costs depends on your fuel and your price. If your fuel costs 10 cent a kWh (that is an example figure; take the real one from your own bill), the C3 house costs about €2,250 a year and the B2 house about €1,250. At 15 cent it is €3,375 against €1,875. The gap is money every year for as long as you live there, and it is the reason a low BER is a reason to bid lower rather than walk away.
How lenders use it
Most lenders offer a green mortgage rate, a lower fixed rate for homes with a BER of B3 or better. The discount is set by each lender and is typically a fraction of a percentage point. Over a long term that is real money: on €300,000 over 30 years, 0.25% off the rate saves about €40 a month. The green mortgage guide explains who qualifies and the green rates page lists the rates, sorted by you, with the CCPC's comparison linked.
Some lenders also offer a green top-up or a lower rate on a loan for works that bring an older home up to B3. You show the BER before and after.
How it affects value
Homes with better ratings tend to sell for more and faster. Agents report it, and the price register shows it in like-for-like streets, but there is no official figure for the premium and it varies by area. The CSO publishes price indices, not BER premiums. What a low rating reliably does is give buyers a number to bid against: the cost of the upgrade. The viewing checklist says what to look for behind the rating.
When a BER is required
- Before a home is advertised for sale or rent. The rating must appear in the advert.
- When a new home is completed.
- Some grants require a BER before and after the works.
A BER lasts ten years. A new one is needed if the home is sold or let again after that, or sooner if you want a better rating shown after a retrofit. Protected structures and some other buildings are exempt. A BER certificate typically costs €225 to €400. A buyer usually pays nothing; the seller has it done before advertising. The BER when selling guide covers the seller's side.
How to check one
Every BER is on SEAI's national register. Ask the agent for the BER number or the MPRN (the number on the electricity meter) and look it up on SEAI's site. You can see the rating, the date, the assessor and the advisory report. A rating from 2016 on a house that has had a heat pump fitted since is out of date and understates the home.
The advisory report
Every certificate comes with an advisory report. It lists the upgrades that would improve the rating, roughly in order of effect: attic insulation, wall insulation, windows, the heating system, controls, solar. It does not price them. It is the first thing to read if you are buying a C or D home and plan to improve it, because it tells you what SEAI's model thinks is missing.
SEAI grants cover most of the items on the list, with a one-stop-shop route that bundles them and manages the work. The SEAI grants guide lists the grants, and the vacant home grant can sit alongside them on a home that has been empty two years.
What a BER does not tell you
- Whether the home is damp, or the roof leaks. That is the survey's job.
- What your bills will be. That depends on you, the weather and the fuel price.
- Whether the heating system works. A ten-year-old boiler and a new boiler of the same type score the same.
- Whether the home is comfortable. A well-insulated home with no ventilation can be stuffy.
Treat the BER as one number among many: what the home needs, the survey, the price register, and the cost of the upgrade.
Where this leaves you
If the home you are looking at is B3 or better, open the green rates page and sort the rates for yourself. If it is C or below, read the advisory report and price the upgrades before you bid. The first-time buyer journey puts the BER in order with the other checks, and you can get quotes for a BER assessor if you need a fresh rating after works.
Questions people ask
What is a good BER rating?
A1 to A3 is the top of the scale and what a new home built to current regulations reaches. B1 to B3 is very good and opens most green mortgage rates. C is average for a home built in the 1990s or 2000s. D to G are older homes with little insulation.
How much does a BER cert cost?
Typically €225 to €400, depending on the size of the home and where it is. Only an assessor on SEAI's register can issue one. It lasts ten years, or until the home is sold or let again with a new one.
Does a BER affect house value?
Homes with better ratings tend to sell for more and faster, and a low rating gives buyers a reason to bid lower. There is no official figure for the difference. The bigger effect is on the mortgage: B3 or better opens green rates at most lenders.
Is a BER required to sell a house?
Yes. A BER must be in place before a home is advertised for sale or rent, and the rating must appear in the advert. Some buildings are exempt, such as protected structures. A seller without one can be fined.
What is the BER advisory report?
A report that comes with every BER certificate listing the upgrades that would improve the rating, in order of effect. It is free with the cert and is the first thing to read if you plan to retrofit.