Heat pump for a new build in Ireland: type, sizing and cost

Decide on your heating system while the house is still on paper, with your designer, before the floor build-up and the electrical supply are fixed. A heat pump is the usual choice for a new Irish house because it counts towards the renewable requirement in Part L and runs at its best in a well-insulated, airtight home.

Is a heat pump required?

No rule names a technology. The nZEB guide sets out the whole-house targets: an Energy Performance Coefficient of no more than 0.30, a Carbon Performance Coefficient of no more than 0.35 and a Renewable Energy Ratio (RER) of at least 20%. Your designer chooses a combination of fabric, heating and renewables that passes the DEAP calculation.

A heat pump helps on all three. It delivers several units of heat for each unit of electricity, and the heat it draws from air, ground or exhaust air counts as renewable energy. That is why it is the default in most designs. An oil or gas boiler is not banned, but it would need other renewables to make up the RER, which usually means more solar panels. See the solar PV guide for that route.

Which type of heat pump?

Type	How it works	Fits	Watch for
Air-to-water	Outdoor unit takes heat from the air and heats water for radiators, underfloor circuits and the hot-water cylinder	Most one-off houses	Noise and position of the outdoor unit, and a defrost cycle in cold weather
Ground-source	Pipework in a borehole or a trench takes heat from the ground	Larger houses on sites with room for a ground loop	Higher installation cost and ground works that must be planned with your site works
Exhaust-air	Takes heat from the ventilation air leaving the house	Small, very airtight, low-demand houses	Limited output; usually needs a mechanical ventilation system designed with it

For most self-builders the real choice is between air-to-water and ground-source. Ground-source costs more to install and its advantage is a steadier source temperature through winter. Ask your designer to show the DEAP result for each, with the extra installed cost, before you decide.

Size it from the heat-loss calculation

A heat pump that is too big cycles on and off and wastes money. One that is too small leaves rooms cold on the coldest days. Your designer or heating engineer should produce a room-by-room heat-loss calculation from the drawings: the insulation levels, window sizes, airtightness target and ventilation strategy. The peak heat loss of the house sets the output you need, and the hot-water demand sets the cylinder size.

Do not accept a size based on floor area alone, or on the installer’s experience with older houses. A new, airtight house needs far less heat per square metre than most people expect. If you change the windows, the insulation or the airtightness target later, ask for the calculation again. The insulation and airtightness test guide explains why those figures move.

Choose the emitters first

A heat pump heats water to a lower temperature than a boiler. The rooms get warm through bigger surfaces rather than hotter ones:

• Underfloor heating spreads low-temperature water through pipes in the screed, or in the slab. It is the usual match for a heat pump in a new build, but it has to be designed into the floor. Decide before the floor slab and screed are specified.
• Oversized radiators work on upper floors, where underfloor heating is awkward. They must be sized for the lower flow temperature. A radiator chosen for a boiler will under-heat the room.
• A mixture is common: underfloor heating downstairs and radiators or underfloor circuits upstairs.

Agree one flow temperature with your designer and installer and write it on the heating drawing. The first-fix guide covers when pipework goes in.

What it costs

There is no official published price for a new-build system, and the costs depend on the design. One electricity supplier publishes a typical installed range for an air-to-water system of €12,500 to €16,000 before any grant, for an existing home. A new, airtight house needs less output, but the price rises with a larger cylinder, underfloor circuits and a ground loop. Treat that range as a starting point for quote comparison, not a budget. Source checked 21 October 2026.

Ask each installer to itemise:

• the heat pump unit and outdoor unit;
• the hot-water cylinder and any buffer tank;
• the underfloor heating or radiators;
• controls, commissioning and the registration of the installation;
• the electrical work, including any upgrade to the supply or consumer unit.

Put the full cost into the build budget. Compare quotes on the same scope and the same design heat-loss figure.

Grants and VAT

SEAI’s heat pump grant is for existing homes built and occupied before 2021, so a new self-build does not qualify. The SEAI grants guide explains the age test and why a quote that deducts a grant is a warning sign. Do not budget for a grant.

Revenue applies the second reduced VAT rate of 9% to the supply and installation of a heat pump heating system from 1 January 2025. See the VAT guide for how that sits beside the 13.5% and 23% rates.

Running cost and the electricity supply

A heat pump moves your heating from fuel to electricity, so your running cost follows your electricity tariff and the house’s heat demand. Ask your designer for the DEAP estimate of delivered energy for space and water heating, and multiply it by the unit price you are quoted. Some suppliers offer a lower rate for homes with a heat pump. Compare tariffs when you move in, not now, because the market changes.

Tell the electrician and the electricity network early that the house will be heated electrically, so the supply capacity is right. The site works guide covers the connection application.

Plan the hot water too

Heating is only part of the load. Hot water is a large share of the energy use of an airtight house, so the cylinder matters. Ask the designer to size it for your household, and to say how often it is heated to the temperature that controls legionella (bacteria that grow in stored warm water). Most systems do this on a weekly cycle using an immersion element or the heat pump itself, which affects running cost. Position the cylinder close to the bathrooms and kitchen so pipe runs are short, and leave space around it for servicing. Cylinder and pipework locations are fixed at first fix, so they belong on the drawings now.

Questions to ask before you sign

1. What is the room-by-room heat-loss figure, and which design temperatures does it use?
2. What flow temperature is the system designed for, and do the emitters match it?
3. Where does the outdoor unit go, and how far is it from a neighbour’s window and from our own bedrooms?
4. Who commissions the system, and what paperwork do I get for the compliance file?
5. What is the price with and without the cylinder and the electrical work?
6. What service plan does the installer offer, and what does it cost each year?

Once the specification is final, check the cover you need before work starts: your site and contract works policy has to be in place on day one. See what cover you need.