Homeowner guide
What a deep retrofit actually costs in Ireland
Updated 2026-09-03 · checked against the sources below
Most answers to this question are a single number with no house attached to it, which is useless: a deep retrofit of a 65 square metre apartment and a 150 square metre detached house are different projects with different grants. This guide works the sums for three typical homes using the current SEAI grant amounts, and shows the gross cost, the grants, the net you actually pay, the annual saving and the payback for each. Every figure is computed from the same engine behind our Home Energy and Grant Report, and every one of them is a range, because that is what an honest estimate looks like before anyone has seen your house.
What counts as a deep retrofit
A deep retrofit is a bundle of measures taken together to lift a home to a B energy rating, rather than one measure at a time. In practice that means the fabric first (attic and wall insulation), then the heating system (usually an air-to-water heat pump replacing oil or gas), then controls, and often windows, doors and ventilation alongside them.
The bundle matters for the money as well as the building. Grants are per measure, so doing several at once compounds them, and the One Stop Shop route applies them at source so you are not funding the whole job and waiting for a refund. Doing measures piecemeal is usually more expensive per unit of improvement and can strand you below the B threshold.
Three worked examples
These are computed for a home built before 2011, taking the full bundle to a B rating. Costs are typical fitted market ranges; grants are the current SEAI amounts for the measures in each bundle. Your own figures will differ - this is the shape of the bill, not a quote.
- D1-rated semi-detached, 115 m2, oil heated, 6 measures: gross EUR 23,800 to EUR 39,850, grants EUR 14,600, net EUR 9,200 to EUR 25,250. Annual saving EUR 1,296 to EUR 2,160, payback 4.3 to 19.5 years.
- E1-rated detached, 150 m2, oil heated, 7 measures including solar PV: gross EUR 30,000 to EUR 49,400, grants EUR 17,972, net EUR 12,028 to EUR 31,428. Annual saving EUR 2,362 to EUR 3,936, payback 3.1 to 13.3 years.
- C3-rated apartment, 65 m2, gas heated, 4 measures: gross EUR 11,300 to EUR 17,350, grants EUR 8,600, net EUR 2,700 to EUR 8,750. Annual saving EUR 580 to EUR 967, payback 2.8 to 15.1 years.
Why the ranges are so wide, and what narrows them
The payback spread on the first example runs from four years to nearly twenty. That is not hedging; it is the honest consequence of two variables nobody can fix in advance. The cost range depends on the state of your house - whether the cavity is empty or already partially filled, whether the attic is accessible, whether the windows are a straight swap or need structural work. The saving range depends on fuel prices over the payback period, which nobody knows.
What narrows both is a BER assessment. It replaces assumptions about your fabric with measurements, and it is grant-funded at EUR 350 on the One Stop Shop route. Getting one before you commission anything is the single highest-value step in the process, and it is the step most people skip.
The One Stop Shop route versus doing it yourself
A registered One Stop Shop project-manages the whole bundle, applies the grants at source and targets the B rating for you. You pay the net figure rather than the gross, and the Home Energy Upgrade Loan (from 2.99%, EUR 5,000 to EUR 75,000 over up to ten years) is available only on that managed route.
Managing it yourself means individual grant applications per measure, paying the gross cost and claiming back, and carrying the coordination risk that the measures actually add up to a B. It can be cheaper in fees and is more work, and the financing option is not available. Neither is wrong; they suit different people.
Eligibility for the deep-retrofit route: the home must have been built and occupied before 2011 and currently rate B3 or lower. The Warmer Homes scheme is a separate, fully funded route for qualifying households and is means tested - it is not something you add to the figures above.
What this does not include
These are indicative measure-set sizings, not a DEAP assessment and not a quote. They exclude anything structural the works uncover, planning permission where a measure needs it (external insulation on a protected structure, some heat pump installations), and the cost of moving out if the works require it. Confirm everything with a registered contractor or BER assessor before committing.
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Quick answers
How much does a deep retrofit cost in Ireland?
For a typical D1-rated semi-detached house of 115 square metres, the full bundle to a B rating costs roughly EUR 23,800 to EUR 39,850 before grants. SEAI grants of about EUR 14,600 bring the net to roughly EUR 9,200 to EUR 25,250. A larger detached house costs more and an apartment considerably less.
How long does a deep retrofit take to pay for itself?
On the worked examples here, between about three and twenty years. The spread is driven by the condition of the house and by fuel prices over the period. A BER assessment narrows it substantially, and it is grant-funded at EUR 350 on the One Stop Shop route.
Do the grants come off the price, or do I claim them back?
On the One Stop Shop route the grants are applied at source, so you pay the net figure. Managing the work yourself means paying the gross cost and claiming each measure's grant back separately.
Does a deep retrofit add to the value of the house?
BER improvements are associated with a resale premium, directionally in the region of 2 to 5 per cent for the uplift modelled here. That is a directional range from published BER price research, not a valuation of your property.
Am I eligible?
The deep-retrofit route requires a home built and occupied before 2011 with a current rating of B3 or lower. Warmer Homes, which is fully funded, is a separate means-tested scheme for qualifying households.
Sources
Related
General guidance, not legal or planning advice. The regulations and your local authority's interpretation bind; conditions and local rules (protected structures, architectural conservation areas, flood zones) can change the answer for a specific property. When in doubt, ask your council for a Section 5 declaration or talk to a planning consultant.