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.
Flats and terraces in Bristol with a small yard or flat roof can suit a compact split outdoor unit. Owners across Bristol can compare split and monobloc designs side by side at a survey in Bristol. In Bristol, a hydrobox often goes in an utility room or garage, with the cylinder alongside.
Who it suits
- Houses with indoor wall space for a boiler-sized hydrobox
- Exposed or frost-prone sites where outdoor water pipes would be a risk
- 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
Grants and rules for heat pumps in England
In England the Boiler Upgrade Scheme gives £7,500 towards an air source heat pump (£9,000 if it replaces oil or LPG, from 21 July 2026 to 31 March 2027), and since 28 April 2026 a valid EPC is no longer needed. The grant is applied for by the MCS-certified installer and shown as a deduction on your quote.
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 Bristol
Here are typical prices for split system heat pumps in Bristol, 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 | After £7,500 grant |
|---|---|---|---|
| 1–2 bedroom flat or small terrace | 4–5 kW | £9,700–£12,750 | £2,200–£5,250 |
| 2–3 bedroom terrace or semi | 5–7 kW | £10,700–£13,750 | £3,200–£6,250 |
| 3 bedroom semi or small detached | 6–9 kW | £12,250–£15,800 | £4,750–£8,300 |
| 4 bedroom detached | 8–12 kW | £14,300–£18,350 | £6,800–£10,850 |
| 5+ bedroom or larger older house | 11–16 kW | £16,850–£22,950 | £9,350–£15,450 |
Installed, inc VAT: unit, cylinder, controls, minor pipework and commissioning.
Towns we cover in Bristol
We cover 6 towns in Bristol for split system heat pumps. Each links to local guide prices and the grant position for England.
| Town | Postcode district | Nearest town | Midwinter daylight |
|---|---|---|---|
| Bristol | BS1 | Clifton | 7 h 50 min |
| Bedminster | BS3 | Bristol | 7 h 50 min |
| Bishopston | BS7 | Westbury-on-Trym | 7 h 50 min |
| Clifton | BS8 | Bristol | 7 h 50 min |
| Fishponds | BS16 | Bishopston | 7 h 50 min |
| Westbury-on-Trym | BS9 | Bishopston | 7 h 50 min |
Split system heat pumps questions
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 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.
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 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.