Air-to-Water vs Air-to-Air Heat Pumps: Which Suits Your Home?

In brief: Both take heat from outdoor air. An air-to-water heat pump heats water for your radiators, underfloor heating and hot water cylinder, so it replaces a boiler. An air-to-air heat pump blows warm or cool air through indoor units, so it heats and cools rooms but does not give you hot water. Most Irish homes replacing a boiler choose air-to-water.

What is the difference between air-to-water and air-to-air?

In brief: The difference is where the heat goes. Air-to-water puts it into water that flows through radiators and a cylinder. Air-to-air puts it straight into room air through wall or ceiling units, the same units used for air conditioning.

	Air-to-water	Air-to-air
Delivers heat through	Radiators, underfloor heating	Wall, ceiling or floor units that blow air
Hot water for showers and taps	Yes, via a cylinder	No
Cooling in summer	Not with radiators	Yes
Replaces a gas or oil boiler	Yes	Only for space heating; you still need hot water from another source
Indoor parts	Cylinder, controls, sometimes new radiators	One indoor unit per room
SEAI grant, house	Up to €14,500	Up to €7,500, plus €2,000 boiler scrappage where it applies
SEAI grant, apartment	Up to €11,500	Up to €7,500, plus €2,000 boiler scrappage where it applies
Common in Irish homes	By far the most common	Less common; more often in apartments and extensions

When should you choose air-to-water?

• You are replacing a boiler: air-to-water is the only one that also covers hot water.
• You have radiators or underfloor heating: the heat pump uses the same pipes. Some radiators may need upgrading, and SEAI pays up to €2,000 towards that in a house.
• You want the full grant: a house leaving oil or gas can get up to €14,500, including the €2,000 boiler scrappage grant. See the SEAI heat pump grant guide.
• You have space for a cylinder: a typical family install needs room for a 200 litre tank.

When should you choose air-to-air?

• You live in an apartment with electric storage heaters: no pipes to reuse, and wall units are quicker to fit than a wet system.
• You want summer cooling: air-to-air is the only heat pump that cools properly.
• You are heating a room the main system does not reach well: an extension, attic conversion or home office.
• Your hot water is already sorted: for example a recent electric cylinder or a solar thermal system.

Can you have both?

In brief: Yes, and it is a common setup in well insulated houses: air-to-water for heating and hot water, plus one or two air-to-air units in bedrooms or a home office for summer cooling.

Which is cheaper to run?

In brief: Both use far less electricity than storage heaters or an electric boiler. Air-to-air often runs slightly more efficiently because it heats air directly, while air-to-water must heat water warm enough for radiators and showers.

Worked example, per 1,000 kWh of heat delivered to your rooms, using example efficiency figures:

System	Example seasonal efficiency (SCOP)	Electricity used
Electric storage heaters	1.0	1,000 kWh
Air-to-water heat pump with radiators	3.5	286 kWh
Air-to-air heat pump	4.0	250 kWh

Multiply the electricity figure by your price per kWh to compare. Real results depend on insulation, settings and tariff, so check the SCOP on the energy label of the exact unit you are quoted.

What about noise and planning?

In brief: Both have an outdoor unit, and most Irish homes can fit one without planning permission if it meets conditions, including a noise limit of 43 dB(A) at the nearest neighbour's boundary and at least 50 cm from the edge of the wall it is mounted on.

Apartments usually also need written permission from the management company before any unit goes on a balcony or facade.

How much does each cost?

In brief: A typical air-to-water install in an Irish 3-bed semi costs around €15,000 to €17,200 before grants. Air-to-air prices depend on how many rooms need an indoor unit, so ask for a per-room breakdown.

See heat pump installation cost in Dublin for a full breakdown.

FAQ

Is an air-to-air heat pump the same as air conditioning? Mostly, yes. It uses the same type of indoor and outdoor units. A heat pump model is designed to heat efficiently in winter as well as cool in summer.

Can an air-to-air heat pump heat a whole house? It can in a small, well insulated home with an open layout, or with one indoor unit per main room. Bedrooms with closed doors need their own unit.

Can I get the boiler scrappage grant with an air-to-air heat pump? Yes, when the air-to-air system replaces an oil or gas boiler, solid fuel heating or electric storage heaters. The radiator upgrade grant does not apply, because there are no radiators.

Which is better for an apartment? Air-to-air if you have storage heaters and want cooling. Air-to-water if the apartment already has a wet central heating system and space for a cylinder.

Get both options quoted

Ask Dublin installers to quote both systems for your home. We add nothing to their prices. Request quotes

Sources: SEAI heat pump system grant, SEAI One Stop Shop grant values, Bord Gáis Energy heat pump guide, Irish Times, September 2026, SEAI conditional planning exemptions.

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