Pulled every Building Energy Rating ever issued in Ireland (1.4 million homes) and ran the numbers on what each rating costs you per year in heating.
Using a 100m² home and ~12c/kWh blended fuel cost:
- A2 home: ~€478/year
- G home: ~€6,818/year
That's roughly a €6,340/year gap between the two ends. Over a 30-year mortgage that's about €190,000 in heating costs for the same house just at a worse rating.
Other things that jumped out:
- only 1.5% of Irish homes are A1-rated
- the bulk are C and D
- homes built before the 2008 building regulations use about 4x more energy per m² than anything built after
SEAI publishes the data behind an ASP NET form button as a 250MB zipped tab-separated file. Pain to work with, so I flattened it into clean CSV and Parquet. Free dataset link in the comments.
Happy to answer any questions about the data.