The cheapest way to heat a home in Ireland

There is no single cheapest way to heat an Irish home, but there is a single correct way to compare the options, and almost nobody uses it. The question is not what a litre of kerosene or a kilowatt hour of gas costs. It is what it costs to deliver one useful kilowatt hour of heat into the room — after the boiler or heat pump has taken its cut.

Get that right and the ranking becomes stable and comparable. Get it wrong and you end up comparing a fuel price to an electricity price, which are not the same kind of number at all.

Step one: energy content

Each fuel carries a different amount of energy per unit sold.

• Kerosene (home heating oil) contains roughly 10 kWh of energy per litre.
• Natural gas is billed directly in kWh, so there is no conversion.
• Electricity is billed directly in kWh.
• Wood, coal and briquettes are sold by weight, with energy content varying widely by moisture and grade.

So a litre of kerosene at, say, 90 cent is about 9 cent per kWh of raw energy. That is the number to compare against a gas or electricity unit rate — not against the litre price, and not against a tank fill.

Step two: efficiency

Now subtract what the appliance wastes.

• An oil boiler, condensing and well serviced, delivers around 85–90% of the fuel’s energy as heat. An older non-condensing boiler can be down at 65–75%.
• A gas boiler, condensing, is similar: high 80s to low 90s in percentage terms, though only if the return water temperature is low enough for it to actually condense — many are run too hot to do so.
• Direct electric heating — panel heaters, immersions, plug-in radiators — is 100% efficient. Every unit you buy becomes heat.
• A heat pump is the outlier. It moves heat rather than creating it, so it delivers roughly 2.5 to 4 kWh of heat per kWh of electricity consumed. That ratio is the seasonal coefficient of performance, and it falls in cold weather and in poorly insulated houses.

Divide your cost per raw kWh by the efficiency and you get cost per useful kWh. This is where the picture changes completely: electricity at three or four times the unit price of gas is roughly level with it once a heat pump’s COP of 3 is applied, and direct electric heating is far and away the most expensive option in the country.

Step three: the standing costs

Fuel is not the whole bill.

Natural gas carries a standing charge whether you burn anything or not, plus carbon tax — currently about 1.25 cent per kWh including VAT on natural gas, rising with each Budget. Both gas and electricity carry VAT at the reduced 9% rate, and electricity additionally carries the PSO levy, a fixed government charge of roughly €19 a year that is identical on every plan.

Heating oil has no standing charge and no meter, but it does have a minimum order — most distributors will not deliver under 200 or 300 litres — and it requires several hundred euro of capital sitting in a tank in the garden. That is a real cash-flow difference even when the per-kWh cost is competitive.

Heat pumps have the largest capital cost by far: an installation is typically five figures, usually alongside insulation and radiator upgrades that the system needs to work efficiently. SEAI grants offset part of it. Whether it pays back depends on the fabric of the house more than on any energy price.

Where the options usually land

For a typical Irish house on today’s prices, the broad ordering by running cost per useful kWh is:

1. Heat pump in a well-insulated house — cheapest to run, most expensive to install.
2. Natural gas — competitive and convenient, but only if the street has a gas main.
3. Home heating oil — usually close to gas, and the price is volatile in both directions. See current heating oil prices by county.
4. Solid fuel — sometimes cheap per kWh, but efficiency in an open fireplace is dismal and smoky-fuel regulations now restrict what can be sold.
5. Direct electric heating — reliably the most expensive way to heat a house in Ireland, by a wide margin, and the reason electrically-heated homes have the highest bills in the country.

That ordering shifts with prices. Kerosene moves week to week with crude oil; gas moves with the wholesale market; electricity moves more slowly but in larger steps. The ordering that does not shift is the one at each end: heat pumps in an insulated house are always cheap to run and direct electric heating is always dear.

The cheapest kilowatt hour is the one you do not buy

Every comparison above is dominated by a variable nobody sells you: how much heat the house loses.

An uninsulated 1970s semi can use three times the energy of the same house after attic insulation, cavity fill and draught-proofing. Insulation is the only intervention that improves every fuel option simultaneously, and it is the only one whose payback does not depend on which way energy prices move. SEAI grants cover a substantial share of the cost for most measures, and attic insulation in particular has a payback measured in a small number of years.

Below insulation, the cheap wins are the boring ones: turn the flow temperature on a condensing boiler down so it actually condenses, service the boiler annually, put the heating on a timer rather than leaving it on, fit thermostatic valves and heat rooms you use, and drop the thermostat by one degree.

What to do next

If you heat with oil, the practical saving is in when and how much you buy — see our guide to reading a heating oil quote, and check oil prices in your county before ordering. If you heat with gas, the standing charge and carbon tax mean the plan you are on matters as much as your usage; compare on the gas price comparison. If you heat with electricity, whether directly or via a heat pump, your tariff is doing most of the work — a heat pump on a timer is exactly the shiftable load that makes a time-of-use tariff pay, and the electricity comparison will rank plans on your own usage.