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 Renfrewshire and Inverclyde can avoid outdoor water pipes altogether with a split system. In Renfrewshire and Inverclyde, a hydrobox often goes in an utility room or garage, with the cylinder alongside. In Renfrewshire and Inverclyde homes where the clearest unit position is away from the plant cupboard, a split system allows a longer route indoors.
Who it suits
- Exposed or frost-prone sites where outdoor water pipes would be a risk
- Owners who would rather not use glycol or anti-freeze valves
- Houses with indoor wall space for a boiler-sized hydrobox
- Small yards, roofs or balconies that suit a more compact outdoor unit
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 Renfrewshire and Inverclyde, 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 Renfrewshire and Inverclyde
These are guide prices for Renfrewshire and Inverclyde, installed and including VAT. Your final price is fixed in a written quote after the survey and depends on the heat loss of the house, the radiators that need changing and where the unit goes.
| Home | Typical size | Installed guide price |
|---|---|---|
| 1–2 bedroom flat or small terrace | 4–5 kW | £9,500–£12,500 |
| 2–3 bedroom terrace or semi | 5–7 kW | £10,500–£13,500 |
| 3 bedroom semi or small detached | 6–9 kW | £12,000–£15,500 |
| 4 bedroom detached | 8–12 kW | £14,000–£18,000 |
| 5+ bedroom or larger older house | 11–16 kW | £16,500–£22,500 |
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 Renfrewshire and Inverclyde
We cover 10 towns in Renfrewshire and Inverclyde for split system heat pumps. Each links to local guide prices and the grant position for Scotland.
| Town | Postcode district | Nearest town | Midwinter daylight |
|---|---|---|---|
| Paisley | PA2 | Barrhead | 6 h 59 min |
| Greenock | PA15 | Gourock | 6 h 57 min |
| Newton Mearns | G77 | Barrhead | 7 h 00 min |
| Renfrew | PA4 | Erskine | 6 h 58 min |
| Barrhead | G78 | Paisley | 6 h 59 min |
| Johnstone | PA5 | Bridge of Weir | 6 h 59 min |
| Erskine | PA8 | Renfrew | 6 h 58 min |
| Bridge of Weir | PA11 | Johnstone | 6 h 59 min |
| Gourock | PA19 | Greenock | 6 h 57 min |
| Port Glasgow | PA14 | Greenock | 6 h 58 min |
Split system heat pumps questions
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.
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.
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.
Do I need an F-gas engineer for a split heat pump?
Yes. Split systems usually use a fluorinated refrigerant such as R32, so installing, servicing or repairing the refrigerant circuit must by law be done by an F-gas certified engineer. That covers joining the refrigerant pipes, testing them for leaks and charging the system. Your quote sets out who carries out each part of the installation, including the refrigerant work.