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What a new oil or gas boiler actually changes

A new boiler makes the same heat from less fuel. It does nothing about the heat the house is losing, and there is no grant for one.

What a boiler does

A boiler burns fuel and hands the heat to the water going round your radiators. How much of the fuel actually reaches the water is the boiler's efficiency, and that is the only thing a new one changes.

The gap is real. SEAI's fuel comparison assumes a gas boiler at 90%, with condensing models running anywhere from 85 to 97%, and an oil boiler at 70%, with a range of 60 to 75%. An old oil boiler at the bottom of that range wastes nearly a third of every litre it burns. Replacing it is a genuine improvement.

It is also the end of the improvement. The new boiler heats the same rooms through the same walls under the same cold attic, and it burns the same fuel at the same price per litre.

What it fixes and what it leaves alone

A new boiler Insulation Controls A heat pump
Heat the house loses unchanged less unchanged unchanged
Fuel burned per unit of heat less unchanged unchanged a different fuel entirely
Heat you make when nobody's home unchanged unchanged far less unchanged
Cost of a unit of heat oil 18.0c, gas 14.4c — — 9.8c
Grant none see the insulation pages €700 €4,500 to €6,500 for the unit, €1,000 to €2,000 for pipework and €4,000 for leaving oil or gas
Reliability new kit, new warranty nothing to break nothing much to break new kit, new warranty

Assumed efficiencies, SEAI Domestic Fuel Cost Comparison, 2026-07-01 edition: gas boiler 90% (condensing 85–97%), oil boiler 70% (60–75%), stove 50% (50–80%). Useful c/kWh: gas 14.4c, oil 18.0c, bulk LPG 25.2c, heat pump 9.8c at SPF 3.5. No grant exists for a fossil-fuel boiler: S.I. No. 749 of 2024, in force 1 January 2025, transposing Article 17(15) of Directive (EU) 2024/1275.

Is it right for a house like yours?

What kind of home?
When was it built?
What's the energy rating?

Your cert may say B2 — that's a B on the new scale.

How is it heated?

A heat pump runs on electricity. Pick "Heat pump" if you have one.

A 1990s detached house on oil, rated CEnergy rating C

Grants you’d get
€12,500
It costs about
€16,500
You pay
€4,000 – €4,500
Saves you each year
about €820
Pays for itself in
about 7 years

The commonest home on file — 47,829 like it. Change an answer above for yours.

Modelled, not observed payments. Middle case €4,519; a quarter of these homes are over €8,930. Repaid in 7–13.4 years. Confidence 0.9.

Or see who is registered in your county
Show what’s included

This is the job list that suits most homes like yours (4 in 10). The money above is the middle of every route we priced, so it will not add up to this list exactly.

  • Is the house warm enough to hold the heat? — SEAI's test before they'll fund a heat pump. The insulation steps are usually what gets you through.

    Heat Loss Indicator ≤ 2.3 W/K·m² after fabric works. 29% of homes like yours already pass. Assessment about €276, grant €350 through a One-Stop-Shop.

    Costs about €280 · grant €350 · the grant covers it

  • Heat pump — replaces the boiler, runs on electricity, pulls heat from the outside air. An outdoor unit the size of a large suitcase, bigger radiators in some rooms, three to five days. Runs cooler for longer — the house feels even, not blasted.

    Air-to-water, SPF 3.5 heating / 2.5 hot water. Cost €16,832 · grant €6,500 + €4,000 (replacing oil/gas/coal) + €2,000 pipework + €700 controls = up to €13,200 · you pay from €3,632. 9.8c per kWh of heat vs gas 14.4c / oil 18.0c.

    Costs about €16,500 · grant €6,500 · you pay €10,000

  • The paperwork — assessment first, grant approval, then the work, then a new energy cert, then the grant is paid. A One-Stop-Shop does all of it and takes the grant off the bill.

    Order is mandatory — work started before approval is not eligible. Energy cert €276, assessment grant €350 through a One-Stop-Shop. Typically 3–6 months end to end (estimate).

    Costs about €280 · grant €350 · the grant covers it

Where the saving comes from — and where it stops

Think of the bill as two numbers multiplied: how much heat the house needs, and how dear each unit of that heat is. A boiler only touches the second one, and only by the size of the efficiency gap — worth having on a bad old boiler, worth little on a decent one.

Insulation attacks the first number, and it keeps working for forty years without being serviced. That is why the order of work on every other page here starts with the roof. If money is tight, the roof and the walls will do more for the same euro than a boiler swap will, and they leave the house ready for whatever heats it next.

When a new boiler is still the right call

Three cases, honestly.

The boiler has died and the house is cold. Heat now beats a plan for March.

The house is nowhere near ready for a heat pump and won't be for years — solid walls, single glazing, no money for fabric work yet. A heat pump forced into that house runs badly and costs a fortune to run.

There's no realistic route to the electric option: no space for an outdoor unit, a flat where the plumbing isn't yours to change, a rented house you don't own.

In all three, take the controls grant while the system is open. It is the one piece of public money still on the table, and it is worth €700.

Common questions

Is there a grant for a new gas or oil boiler?
No. SEAI do not grant-aid a new or replacement fossil-fuel boiler, and it is not a rule they can bend for an emergency. Since 1 January 2025 Irish law forbids public bodies from putting money toward installing a stand-alone fossil-fuel boiler. You can still buy one and still fit one; the State just will not help pay for it.
Are oil and gas boilers being banned?
Not in existing homes, and no date has been set for one. The binding rule is the funding ban that started in January 2025. The often-quoted 2040 comes from a reporting template in an EU directive, where national plans have to describe a phase-out "with a view to" that year. New houses are a different story and it is already settled — building standards made fossil boilers impractical in new homes years ago.
My boiler died in January. What should I do?
Get it looked at before you replace it, because a repair can be grant-aided where a replacement cannot, and a failed part on a twelve-year-old boiler is often worth fixing. If it does have to go, take the heating controls grant at the same time — the system is already open and the work is already being done. Do not let a cold week decide the next twenty years of heating.

Where to next

Where this comes from

Last checked 2026-09-08.