Not “what grant do I get” — the question that actually stalls people: will it cost less to run than my boiler? Put in your heat demand and your real fuel prices. This compares the honest annual running cost per fuel and shows why the answer lives or dies on two things: your heat pump's efficiency (SCOP) and your electricity tariff.
Running cost is annual heat demand × cost per useful kWh. The demand is the same whatever fuel makes the heat — so this number scales every column equally.
A rough demand figure is fine — you can read your real kerosene litres or gas kWh off last year's bills for a sharper answer. A typical Irish 3-bed semi lands around 12,000–15,000 kWh.
Use the prices you actually pay — they move constantly and they decide the whole comparison. Oil is bought by the litre; gas is billed per kWh.
Your current heating fuelA heat pump's cost per useful kWh is your electricity rate divided by its SCOP — the average units of heat it delivers per unit of electricity over a year. SCOP is the whole ballgame, and it's set by how well the system is designed and how well your house holds heat.
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| Fuel | c / useful kWh | Per year |
|---|
Fuel energy content used: kerosene 10.35 kWh/litre; mains gas billed per kWh already; direct electric is 100% efficient at the meter but expensive per unit. The boiler-efficiency figure is how much of the fuel you buy actually reaches the room.
If your house is cold and leaky, a heat pump will run at a low SCOP and can genuinely cost more than oil to run — the technology isn't the problem, the fabric is. That's why the honest order is insulate first, heat pump second: attic and wall insulation (each with their own SEAI grant) drop your heat demand and lift the SCOP a heat pump can hit, turning a “dearer to run” result into a comfortable win. Beyond running cost, a heat pump also removes the ~2 tonnes of CO₂ a year an oil boiler emits and sidesteps the carbon tax that's added to kerosene and gas every budget — a cost that only climbs. This tool answers running cost; for the €12,500 grant maths, use the SEAI heat pump grant checker.
SEAI heat pump grant — official terms →Your running cost hinges on system design (emitter sizing, flow temperature, commissioning). Compare quotes from SEAI-registered installers who'll design for a real, high SCOP — not just drop a box in.
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Every euro figure is computed only from the prices you enter — the tool invents no fuel prices. The fixed conversions are planning anchors: kerosene at 10.35 kWh/litre; boiler efficiency you choose (70–90%); mains gas billed per kWh; direct electric 100% efficient at the meter; and the heat pump's cost = your electricity rate ÷ the SCOP you select, with a ~26c blended rate modelled for a heat-pump smart tariff. Standing charges are excluded on all fuels (they roughly wash out and vary by supplier). SCOP is the single biggest lever and is genuinely uncertain until a system is designed and commissioned — treat the result as “which way does this point, and by how much,” not a precise bill. Figures last reviewed July 2026 — re-check current kerosene, gas and electricity prices before you rely on them.
Usually yes, but often by less than people expect — and only if it's a decent system in a reasonable house. At a typical SCOP of 3.7 and standard day-rate electricity, a heat pump beats an oil boiler by roughly 15–25% on running cost. Push the SCOP up (better insulation, correctly sized radiators) or move onto a heat-pump smart tariff and the gap widens a lot. Let the SCOP fall (leaky house, undersized emitters) and the advantage shrinks or vanishes. The calculator above shows exactly where your numbers land.
This is the honest hard one: at standard electricity rates, often not. Mains gas is Ireland's cheapest heating fuel per useful kWh, so a heat pump on a plain day rate can actually cost a little more to run than a good gas boiler. The heat pump wins on gas when you combine a high SCOP with a smart tariff, and it always wins on carbon and on future fuel-price direction — but if someone tells you a heat pump is automatically cheaper than gas to run, be sceptical and check your own figures here first.
SCOP (Seasonal Coefficient of Performance) is the average amount of heat a heat pump delivers per unit of electricity across a whole year. A SCOP of 3.7 means 3.7 kWh of heat for every 1 kWh of electricity. Because your running cost is electricity price ÷ SCOP, a system running at 4.2 versus 2.8 costs a third less to run for the same warmth. SCOP isn't a fixed spec — it's the result of insulation, radiator/underfloor sizing, flow temperature and commissioning. A cheap install that undersizes the emitters is the classic cause of a disappointing SCOP and a nasty electricity bill.
Two reasons, both financial. First, insulation cuts your heat demand, so every fuel column — including the heat pump — shrinks. Second, a warmer, tighter house lets the heat pump run at a lower flow temperature and a higher SCOP, which is the difference between a heat pump that's cheaper than oil and one that isn't. Putting a heat pump into a cold, leaky house is the single most common way to end up with a big bill and a bad opinion of the technology. Attic and wall insulation each have their own SEAI grant and usually pay back faster than the heat pump does.
Materially, yes, if you have a smart meter. Heat pumps are well suited to time-of-use tariffs because you can pre-heat the house and the hot-water cylinder during cheap overnight hours and coast through the expensive peak. A good chunk of the annual load can shift into the cheap window, pulling the effective electricity rate down well below the day rate — which is what tips the heat pump clearly ahead of oil, and can even get it ahead of gas. The smart-tariff toggle above models this with a blended rate.
No — this tool compares running costs only, the year-to-year fuel bill. The upfront cost (typically €13,000–€18,000 for an air-to-water retrofit, less the SEAI grant of up to €12,500) is a separate question. If a heat pump only breaks even with your current boiler on running cost, the payback on the install itself will be long, and the honest reasons to switch become comfort, carbon and future-proofing rather than pure savings. For the grant and net-cost side, see the SEAI heat pump grant checker.
They're left out of the main comparison because their pricing doesn't reduce cleanly to a single Irish unit rate the way oil, gas and electricity do — solid fuel and LPG in particular vary hugely by format and supplier, and pretending otherwise would be false precision. As a rough guide, LPG and bottled gas are among the dearest per useful kWh (usually dearer than oil), so a heat pump beats them comfortably; wood pellets can be competitive if you buy in bulk. If you're on one of these, treat the oil column as a conservative stand-in and know the heat pump case is generally stronger, not weaker.