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.
In Northamptonshire, a hydrobox often goes in an utility room or garage, with the cylinder alongside. In Northamptonshire homes where the clearest unit position is away from the plant cupboard, a split system allows a longer route indoors. Installers covering Northamptonshire keep refrigerant routes neat and protected along the outside wall.
Who it suits
- Small yards, roofs or balconies that suit a more compact outdoor unit
- Houses with indoor wall space for a boiler-sized hydrobox
- Owners who would rather not use glycol or anti-freeze valves
- Exposed or frost-prone sites where outdoor water pipes would be a risk
Grants and rules for heat pumps in England
Homes in Northamptonshire can use the Boiler Upgrade Scheme, which takes £7,500 off the cost of an air source heat pump when it replaces fossil-fuel or electric heating. Replacing oil or LPG heating qualifies for £9,000 for installations from 21 July 2026 to 31 March 2027, and air-to-air systems for £2,500. The MCS-certified installer named in your quote applies for the grant and deducts it from the price.
Installing heat pumps is zero-rated for VAT across the UK until 31 March 2027. Since 29 May 2025, permitted development in England allows up to two air source heat pumps on a house, each up to 1.5 m³, with no blanket 1 m boundary rule — the installation must still meet the MCS planning standards, including the noise check. Listed buildings, flats and some conservation-area positions need extra consent, which we check at survey.
Split system heat pumps prices in Northamptonshire
The ranges below are typical installed prices for homes in Northamptonshire, including VAT. A survey sets the exact figure, because two similar-looking houses in Northamptonshire can need quite different radiators and pipework.
| Home | Typical size | Installed guide price | After £7,500 grant |
|---|---|---|---|
| 1–2 bedroom flat or small terrace | 4–5 kW | £9,500–£12,500 | £2,000–£5,000 |
| 2–3 bedroom terrace or semi | 5–7 kW | £10,500–£13,500 | £3,000–£6,000 |
| 3 bedroom semi or small detached | 6–9 kW | £12,000–£15,500 | £4,500–£8,000 |
| 4 bedroom detached | 8–12 kW | £14,000–£18,000 | £6,500–£10,500 |
| 5+ bedroom or larger older house | 11–16 kW | £16,500–£22,500 | £9,000–£15,000 |
Installed, inc VAT: unit, cylinder, controls, minor pipework and commissioning.
Towns we cover in Northamptonshire
We cover 10 towns in Northamptonshire for split system heat pumps. Each links to local guide prices and the grant position for England.
| Town | Postcode district | Nearest town | Midwinter daylight |
|---|---|---|---|
| Northampton | NN1 | Wellingborough | 7 h 42 min |
| Corby | NN17 | Desborough | 7 h 39 min |
| Kettering | NN16 | Desborough | 7 h 40 min |
| Wellingborough | NN8 | Rushden | 7 h 41 min |
| Rushden | NN10 | Wellingborough | 7 h 41 min |
| Daventry | NN11 | Towcester | 7 h 42 min |
| Brackley | NN13 | Towcester | 7 h 44 min |
| Desborough | LE16 | Kettering | 7 h 40 min |
| Oundle | PE8 | Corby | 7 h 39 min |
| Towcester | NN12 | Northampton | 7 h 43 min |
Split system heat pumps questions
How far apart can the outdoor unit and hydrobox be?
It depends on the model: each manufacturer sets a maximum refrigerant pipe length and height difference, and longer runs may need extra refrigerant. In practice a split system allows more flexibility than a monobloc's water pipes, so the outdoor unit can often sit on the far side of a house, on a flat roof or round a corner. The survey measures the actual route.
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.
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.
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.