Heat pump options
Our house is from 1974, with radiators sized for 55°C and a roof insulated in 2019. The gas boiler is 21 years old and due for replacement.
Working notes, not advice. Costs are rough ranges from articles and installer websites, before any subsidy. Confirm everything with installers and an energy adviser.
What matters for our house
- Flow temperature. Heat pumps are most efficient at low flow temperatures, around 35 to 45°C. Our radiators were sized for 55°C, so a few rooms may need larger radiators to stay warm on the coldest days.
- Heat loss. The roof is done, but the walls are uninsulated and the windows are from the 1990s. A room-by-room heat loss calculation is the first real step; installers should do one before quoting.
- Space. An outdoor unit needs a spot with airflow and some distance from the neighbours' windows. The side of the garage looks like the best place.
Compared
| Type | Est. cost | Fit |
|---|---|---|
| Air to water | €12–18k | best |
| Hybrid | €9–14k | good |
| Ground source | €25–35k | costly dig |
- Air to water: works with our radiators if two or three are upsized. The outdoor unit makes some noise.
- Hybrid: a small heat pump plus a gas boiler for cold days. Cheaper now, but keeps a gas connection.
- Ground source: most efficient and quiet, but needs boreholes or a large trench, and the garden is small.
Running costs
A heat pump typically delivers three to four units of heat per unit of electricity. Whether it beats gas depends on our electricity and gas prices. With a heat pump tariff it likely comes out cheaper per year, but by how much depends on the heat loss numbers.
Next steps
- Get two quotes for air to water. Ask each installer for a heat loss calculation and their proposed flow temperature.
- Check the 2026 subsidy rules (see below).
- Ask which radiators they would replace, and what that adds to the cost.
- Look into a heat pump electricity tariff.
Questions for installers
- What flow temperature do you design for, and what efficiency do you expect?
- Where would the outdoor unit go, and how loud is it at night?
- Do you handle the subsidy application, or do we?
2026 subsidy rules
Added this week. Summarised from the program's public pages; the details change, so check the current rules before signing anything.
- A base grant covers a share of eligible costs for replacing a fossil heating system, with extra percentage points for replacing an old gas boiler.
- There is a cap on eligible costs per home, so the grant does not scale past a certain project size.
- An income-based bonus applies below a household income threshold.
- The application usually has to be filed before the contract is signed. Some programs allow signing a contract with a clause that makes it conditional on approval.
- Installers must be registered, and the unit has to meet an efficiency and refrigerant requirement.
For us: ask both installers whether their quote qualifies, and do not sign until the application is in.