A split system heat pump is an air-to-water heat pump in two parts: an outdoor unit that collects heat from the air, and an indoor unit called a hydrobox where that heat is passed into the water for your heating and hot water. The two are connected by insulated refrigerant pipes rather than water pipes, so there is no water outside to freeze.
Properties on exposed sites around Edinburgh and the Lothians can avoid outdoor water pipes altogether with a split system. Installers covering Edinburgh and the Lothians keep refrigerant routes neat and protected along the outside wall. In Edinburgh and the Lothians homes where the clearest unit position is away from the plant cupboard, a split system allows a longer route indoors.
Who it suits
- Houses with indoor wall space for a boiler-sized hydrobox
- Homes where the outdoor unit must sit some distance from the plant space
- Small yards, roofs or balconies that suit a more compact outdoor unit
- Owners who would rather not use glycol or anti-freeze valves
Grants and rules for heat pumps in Scotland
In Scotland, heat pump funding comes through Home Energy Scotland rather than the Boiler Upgrade Scheme: a grant of up to £7,500 (up to £1,500 extra for eligible rural and island homes) and an optional interest-free loan of up to £7,500. For a home in Edinburgh and the Lothians, apply and receive the written offer before the installation date is fixed.
There is no VAT on installing a heat pump anywhere in the UK, Scotland included, until 31 March 2027. Scottish permitted development rules and building standards apply, and the surveyor checks the unit position and any listed or conservation-area constraints.
Split system heat pumps prices in Edinburgh and the Lothians
Here are typical prices for split system heat pumps in Edinburgh and the Lothians, installed and including VAT. Use the guide price tool for a figure based on your home, then a survey confirms it in writing.
| Home | Typical size | Installed guide price |
|---|---|---|
| 1–2 bedroom flat or small terrace | 4–5 kW | £9,700–£12,750 |
| 2–3 bedroom terrace or semi | 5–7 kW | £10,700–£13,750 |
| 3 bedroom semi or small detached | 6–9 kW | £12,250–£15,800 |
| 4 bedroom detached | 8–12 kW | £14,300–£18,350 |
| 5+ bedroom or larger older house | 11–16 kW | £16,850–£22,950 |
Installed, inc VAT: unit, cylinder, controls, minor pipework and commissioning. In Scotland, Home Energy Scotland grants of up to £7,500 and interest-free loans may reduce the cost.
Towns we cover in Edinburgh and the Lothians
We cover 12 towns in Edinburgh and the Lothians for split system heat pumps. Each links to local guide prices and the grant position for Scotland.
| Town | Postcode district | Nearest town | Midwinter daylight |
|---|---|---|---|
| Edinburgh | EH2 | Musselburgh | 6 h 57 min |
| Livingston | EH54 | Broxburn | 6 h 58 min |
| Musselburgh | EH21 | Dalkeith | 6 h 57 min |
| Bathgate | EH48 | Livingston | 6 h 58 min |
| Bonnyrigg | EH19 | Dalkeith | 6 h 58 min |
| Penicuik | EH26 | Bonnyrigg | 6 h 59 min |
| Broxburn | EH52 | Livingston | 6 h 58 min |
| Dalkeith | EH22 | Bonnyrigg | 6 h 58 min |
| Dunbar | EH42 | North Berwick | 6 h 57 min |
| Haddington | EH41 | North Berwick | 6 h 57 min |
| Linlithgow | EH49 | Bo'ness | 6 h 57 min |
| North Berwick | EH39 | Haddington | 6 h 56 min |
Split system heat pumps questions
Is a split system more efficient than a monobloc?
Not inherently. Efficiency depends far more on design, meaning correct sizing, low flow temperatures and good controls, than on whether the unit is split or monobloc. A split system can avoid the heat loss and glycol of a long outdoor water run, which helps in certain layouts. The survey estimates seasonal efficiency for the specific units proposed, so you can compare like for like.
Can a split system replace my combi boiler?
Yes, but like any air-to-water heat pump it needs a hot water cylinder, because it does not heat water instantly. The hydrobox can sometimes go where the combi was, with the cylinder in a cupboard, utility room or garage. Integrated units combining both are useful where one larger space is available. The survey checks what fits before the design is finalised.
How big is a hydrobox?
A hydrobox is typically about the size of a wall-mounted boiler, though sizes vary by make and model. It needs wall space near the cylinder with room around it for servicing and pipe connections. Some manufacturers combine the hydrobox and cylinder in a single floor-standing unit similar in size to a tall fridge-freezer, which can suit a utility room or garage.
Is a split system eligible for the Boiler Upgrade Scheme?
Yes. A split air-to-water heat pump counts as an air source heat pump under the scheme, so in England and Wales eligible owners of existing homes can receive £7,500, or £9,000 when replacing oil or LPG within the published dates. The MCS-certified installer applies for you. Scotland's Home Energy Scotland funding is separate, and Northern Ireland has no dedicated homeowner grant at present.