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Data story · Payback · Our model, re-run 5 Oct 2026

From a G, the work to reach a B pays for itself fastest: about 4 years

We worked out the cheapest grant-eligible route to a B for every common kind of Irish home, at SEAI’s median prices and today’s grants. From a G it pays for itself in about 4 years; from a D, about 8 years, the slowest. Our model, re-run 5 Oct 2026.

A cottage built before 1970

A cottage built before 1970: the kind of house that fills the F and G rows.

Semi-detached cottage in Geashill, County Offaly · A.-K. D. · CC0 1.0 (public domain dedication)

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Our model: each figure is the middle home type at that grade, weighted by certificates.

4 years

From a G: the quickest

Our model · built 5 Oct 2026 · 802,344 certificates

Our model

8 years

From a D: the slowest

Our model · built 5 Oct 2026 · 802,344 certificates

Our model

5 years

From a C, mostly a heat pump

Our model · built 5 Oct 2026 · 802,344 certificates

Our model

195

Home types modelled, from C to G

SEAI BER file 8 Sep 2026

Our model

Updated · grants checked · BER file · model 5 Oct 2026 · prices SEAI H1 2026 · How we know · Corrections

Where this sits · the heat chain

Heat leaves through the walls, roof, floor, windows and draughts. The heating puts it back. A BER adds it all up.

  1. Fabricwalls, roof, floor, windows
  2. Airdraughts and ventilation
  3. Heatheat pump or boiler, radiators, controls
  4. Usebills, comfort, the BER
  1. The idea behind itA BER is a standard calculation
  2. You are hereWhich homes pay back fastest
  3. Next questionHow do you get a house like yours to a B?

How fast the work to a B pays for itself, by starting grade

After today's grants, at SEAI's median prices and fuel prices. Our model

Figure 1Our model

From a G, about 4 years; from a D, about 8 years

From C 5 years, D 8 years, E 7 years, F 6 years, G 4 years. You pay after grants, in the middle: from G €16,900, from D €9,200.

  1. Energy rating C5 years
  2. Energy rating D8 years
  3. Energy rating E7 years
  4. Energy rating F6 years
  5. Energy rating G4 years

Each row is a starting grade. The bar is how many years the yearly saving takes to cover what you pay after grants, for the middle home type at that grade, weighted by certificates. It uses the cheapest grant-eligible route to a B, SEAI's median price for each job, the grants in force on the day we re-ran the model, and SEAI's fuel prices. Black rows: the quickest and the slowest.

EstimateOur model on SEAI's BER file, 802,344 certificates across 195 home types. Standard occupancy, so a real household's bills and payback differ.

Sources: fixmyber model (pipeline/inputs/metric_prototype.py) on the SEAI BER file, 8 Sep 2026 · SEAI, Median costs of individual energy upgrades, Jan-Jun 2026 (H1 2026), 2026

The numbers
The numbers behind figure 1
FromBefore grantsGrantsYou payPays for itself inGets to B
C€16,700€14,500€2,500about 5 years86%
D€28,000€19,000€9,200about 8 years78%
E€35,500€21,300€14,200about 7 years67%
F€38,200€22,500€16,900about 6 years54%
G€39,400€25,000€16,900about 4 years31%

Download the data (CSV)

What the route to a B costs before grants

The spread across the home types that start at each grade. Our model

Figure 2Our model

From a C, the cheapest route to a B costs about €16,700 before grants; from a G, about €39,400

In our model the median cost rises from €16,741 (from C) to €39,400 (from G), and the worse the start, the fewer homes the route gets all the way to B: 86% from C, 31% from G.

Modelled cost of the cheapest grant-eligible route to a B, before grants, by starting gradeOur model, across the home types that start at each grade, weighted by certificates. Median, middle half and middle 80%: from C: €16,741 (middle half €16,000–€17,000, 80% €9,025–€19,700); the route gets 86% of these homes to B; from D: €28,004 (middle half €20,165–€28,685, 80% €10,540–€35,625); the route gets 78% of these homes to B; from E: €35,505 (middle half €28,954–€38,185, 80% €14,761–€42,912); the route gets 67% of these homes to B; from F: €38,185 (middle half €37,254–€41,224, 80% €16,276–€45,372); the route gets 54% of these homes to B; from G: €39,400 (middle half €37,254–€42,801, 80% €29,793–€45,290); the route gets 31% of these homes to B. Costs are SEAI median costs per job, before grants.FROM → TO€ BEFORE GRANTS, CHEAPEST ROUTE TO BGETS TO B€0€10k€20k€30k€40k€50kC→B€16,74186%D→B€28,00478%E→B€35,50567%F→B€38,18554%G→B€39,40031%medianmiddle half of home typesmiddle 80%Dashed = our model. Each home type's cost is SEAI's median for the jobs in its route.
Modelled cost of the cheapest grant-eligible route to a B, before grants, by starting gradeOur model, across the home types that start at each grade, weighted by certificates. Median, middle half and middle 80%: from C: €16,741 (middle half €16,000–€17,000, 80% €9,025–€19,700); the route gets 86% of these homes to B; from D: €28,004 (middle half €20,165–€28,685, 80% €10,540–€35,625); the route gets 78% of these homes to B; from E: €35,505 (middle half €28,954–€38,185, 80% €14,761–€42,912); the route gets 67% of these homes to B; from F: €38,185 (middle half €37,254–€41,224, 80% €16,276–€45,372); the route gets 54% of these homes to B; from G: €39,400 (middle half €37,254–€42,801, 80% €29,793–€45,290); the route gets 31% of these homes to B. Costs are SEAI median costs per job, before grants.€ BEFORE GRANTS, CHEAPEST ROUTE TO B€0€10k€20k€30k€40k€50kC→B86% reach B€16,741D→B78% reach B€28,004E→B67% reach B€35,505F→B54% reach B€38,185G→B31% reach B€39,400Dot = median · bands = middle half and 80%of home types. Dashed = our model.

Each row is a starting grade. The dot is the median cost before grants of the cheapest grant-eligible route to B across the home types that start there, weighted by certificates; the dark band is the middle half of home types and the light band the middle 80%. The right-hand column is the share of homes like these that the route gets to B. This is the spread across types of home, not the spread of quotes.

EstimateOur model: data/transitions.json, 195 published home types, 802,344 certificates. Re-run 5 Oct 2026 with the 29 Sep heat pump grant (€14,500 bundle) and each certificate's own electricity factor (1.753 from Feb 2023), so grants and routes are current.

Sources: fixmyber model (pipeline/inputs/metric_prototype.py) on the SEAI BER file, 8 Sep 2026 · SEAI, Median costs of individual energy upgrades, Jan-Jun 2026 (H1 2026), 2026

The numbers
The numbers behind figure 2
FromLowest 10%Lower quarterMedianUpper quarterHighest 10%Gets to B
C → B€9,025€16,000€16,741€17,000€19,70086%
D → B€10,540€20,165€28,004€28,685€35,62578%
E → B€14,761€28,954€35,505€38,185€42,91267%
F → B€16,276€37,254€38,185€41,224€45,37254%
G → B€29,793€37,254€39,400€42,801€45,29031%

The twenty commonest homes

Each one's route to a B, what the grants pay, and how fast it pays for itself. Biggest groups first. Our model

Cost, grant, what you pay and years to pay for itself for the twenty most common Irish homes
HomeHomesThe workGrantYou payPays for itself in
Energy rating C A 1990s detached house on oil, rated C47,829€17,000€14,500€3,200about 5 years
Energy rating C A 1990s semi-detached on gas, rated C37,798€16,700€14,500€2,200about 6 years
Energy rating C A 1990s semi-detached on oil, rated C29,131€16,700€14,500€2,200about 6 years
Energy rating C A 1970s–80s detached house on oil, rated C24,045€19,700€14,500€9,300about 13 years
Energy rating C A 1990s apartment on electric heating, rated C23,787€9,000€9,000nothingstraight away
Energy rating D A 1970s–80s detached house on oil, rated D23,707€36,800€22,300€14,400about 8 years
Energy rating F/G A pre-1970 detached house on oil, rated F/G21,637€41,000€25,000€16,600about 4 years
Energy rating D A 1990s apartment on electric heating, rated D21,468€9,000€9,000nothingstraight away
Energy rating C A 1990s terrace house on gas, rated C20,620€16,000€14,500€1,500about 5 years
Energy rating C A 1990s apartment on gas, rated C19,505€9,000€9,000nothingstraight away
Energy rating C A 1970s–80s terrace house on gas, rated C17,875€16,000€14,500€2,300about 7 years
Energy rating D A 1990s detached house on oil, rated D15,504€30,800€21,000€10,000about 9 years
Energy rating C A pre-1970 terrace house on gas, rated C15,252€16,000€14,500€2,700about 8 years
Energy rating D A pre-1970 terrace house on gas, rated D14,573€28,000€17,900€10,100about 9 years
Energy rating C A 1970s–80s semi-detached on gas, rated C14,454€16,700€14,500€6,300about 9 years
Energy rating D A pre-1970 detached house on oil, rated D13,321€28,300€21,000€7,300about 6 years
Energy rating E A pre-1970 detached house on oil, rated E12,266€35,900€23,000€12,400about 5 years
Energy rating C A 1990s detached house on gas, rated C11,482€19,700€14,500€4,800about 7 years
Energy rating E A pre-1970 terrace house on gas, rated E10,967€35,200€19,700€16,300about 9 years
Energy rating D A 1970s–80s semi-detached on oil, rated D10,819€28,700€19,000€9,200about 9 years

Our model, re-run 5 Oct 2026 · H1 2026 medians (n=23,412 upgrades; OSS n=583) · fuel prices 1 Jul 2026 · BER file 8 Sep 2026

Check first: apartments. SEAI's apartment heat pump grant (up to €11,500) is more than its median apartment job (€9,000), and SEAI won't pay more than the work costs, so the model shows nothing to pay. Ask SEAI how the grant is capped before you count on it.

The data, and how to cite it

Cite as: FixMyBER model of the cheapest grant-eligible route to a B, on the SEAI BER Research Tool (CC BY 4.0) and SEAI’s median costs, re-run 5 Oct 2026. fixmyber.ie/stories/b-league

Quote the figures freely with a link to this page. They are modelled, not measured: say so when you use them.

How we know

Sources

fixmyber model (pipeline/inputs/metric_prototype.py) on the SEAI BER file, 8 Sep 2026 · SEAI, Median costs of individual energy upgrades, Jan-Jun 2026 (H1 2026), 2026

Found a mistake? Every fix is dated on Corrections. Method in full: How we know.

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Updated · grants checked · BER file · model 5 Oct 2026 · How we know · Corrections