When it comes to monoblock vs split heat pump systems, a monoblock is the better choice for most homes in Kent and the South East. It is simpler and usually cheaper to install, and all of its refrigerant is sealed inside one outdoor unit.
A split heat pump makes more sense when the outdoor unit has to sit far from the house, when indoor space allows a second unit, or when you want to avoid running water pipes outside in freezing weather.
Both types are air source heat pumps. Both take heat from the outside air and use it to warm your radiators and hot water, and both qualify for the £7,500 Boiler Upgrade Scheme grant. The difference is where the key parts sit and how heat travels into your home.
At Guscott Heating, we install both monoblock and split air source heat pumps in homes from Maidstone and Canterbury to Tunbridge Wells, Bromley and Brighton. This guide compares the two side by side so you can make the right choice for your home or rental property.
Monoblock vs Split Heat Pump: Key Facts
Monoblock and split heat pumps offer similar heating performance, but differ in their design, installation requirements, space needs and upfront costs. The table below summarises the main differences to help you compare both systems at a glance.
| Factor | Monoblock heat pump | Split heat pump |
| How it works | All key parts in one outdoor unit; water pipes run into the house | Outdoor unit plus an indoor unit (hydrobox), linked by refrigerant pipes |
| Efficiency (SCOP) | Around 3.5 to 4.7 | Around 3.5 to 4.7 |
| Cold weather performance | Very good, but outdoor water pipes need frost protection | Very good, with no water outside to freeze |
| Unit cost | £3,500 to £7,000 | £4,000 to £7,500 including indoor unit |
| Total installed cost | £10,000 to £14,000 | £11,000 to £16,000 |
| Cost after £7,500 grant | £2,500 to £6,500 | £3,500 to £8,500 |
| Running costs (3 bed home) | Around £850 to £1,300 a year | Around £850 to £1,300 a year |
| Reliability | Factory sealed refrigerant circuit, low leak risk | Joints made on site, slightly higher leak risk |
| Indoor space needed | Hot water cylinder only | Cylinder plus a wall mounted indoor unit |
| Distance from house | Best within a few metres | Refrigerant pipes can often run 30 metres or more |
| Installer requirements | MCS certified heating engineer | MCS certified engineer with F Gas certification |
| Servicing and maintenance | Annual service, check antifreeze or frost valves | Annual service, F Gas leak checks on the refrigerant |
| Common refrigerant | R290 (natural, very low climate impact) | Usually R32 |
| Lifespan | 15 to 20 years or more | 15 to 20 years or more |
| Boiler Upgrade Scheme | Eligible | Eligible |
| Best for | Most houses with space for the unit near an outside wall | Homes with little outdoor space near the house, long pipe runs or exposed sites |
All figures are approximate guide prices for a typical 5kW to 10kW system in Kent and the South East, including a hot water cylinder and any radiator upgrades. Your exact price depends on your home’s heat loss.
Not sure which type suits your home? Guscott Heating provides air source heat pump installation across Kent and the wider South East of England, including Maidstone, Ashford, Sevenoaks, Medway, Dartford, Crawley and Guildford. Our engineers will survey your property and recommend the right system. Get in touch today for a free estimate tailored to your location.
Monoblock vs Split Heat Pump: Which Should You Choose?
Whether you should choose a monoblock or split heat pump depends mainly on your outdoor space, indoor space and budget. Use the checklists below to see which fits your home.
Choose a monoblock heat pump if…
- You have space for the outdoor unit close to an outside wall
- You want the lowest installation cost
- You would rather avoid an extra unit taking up space indoors
- You want a natural R290 refrigerant with a very low climate impact
- You are replacing a gas or oil boiler in a typical house, bungalow or semi
Don’t choose a monoblock heat pump if…
- The only place for the outdoor unit is far from the house, such as the end of a long garden
- Water pipes would need long outside runs that are hard to protect from frost
- Your home is on an exposed spot, such as the North Downs or the Kent coast, where long outdoor pipes would lose a lot of heat
Choose a split heat pump if…
- The outdoor unit needs to sit well away from your home
- You have room indoors for a wall mounted unit about the size of a combi boiler
- You want no water pipes outside the house at all
- You have a flat or a home with restricted outdoor space where a smaller outdoor unit helps
Don’t choose a split heat pump if…
- Indoor space is tight and the cylinder already fills your only cupboard
- You want the simplest installation with the lowest upfront cost
- You would prefer a system that does not need F Gas leak checks
Monoblock vs Split Heat Pump: What Are the Pros & Cons?
The pros and cons of monoblock vs split heat pump systems mostly come down to simplicity versus flexibility. Here is how each type stacks up.
Pros & Cons of Monoblock Heat Pumps
| Pros | Cons |
| Lower installation cost | Outdoor water pipes need frost protection |
| Quicker, simpler installation | Unit needs to sit close to the house |
| Refrigerant sealed at the factory, so leaks are rare | Some heat is lost through outdoor pipework on longer runs |
| No indoor unit, saving cupboard space | Outdoor units can be larger and heavier |
| Most models use R290, a natural refrigerant | Fewer placement options on tricky plots |
| No F Gas engineer needed to install | Antifreeze, if used, needs checking over time |
Pros & Cons of Split Heat Pumps
| Pros | Cons |
| Outdoor unit can sit far from the house | Higher installation cost |
| No water pipes outside, so no freezing risk | Needs an F Gas certified engineer to install and service |
| Smaller outdoor unit in many cases | Indoor unit takes up wall space |
| Less heat lost on long pipe runs | Refrigerant joints made on site carry a small leak risk |
| Flexible for awkward plots and flats | Most use R32, which has a higher climate impact than R290 |
| Good choice for exposed or very cold sites | Fewer installers offer split systems |
Monoblock vs Split Heat Pump: How Do They Compare Head to Head?
Monoblock and split heat pumps are closely matched in terms of efficiency and lifespan, but they differ in installation, cost and practical advantages. The following sections compare each factor in detail and highlight which system comes out ahead in each category.
Design and How They Work
A monoblock heat pump holds the compressor, refrigerant and heat exchanger in one outdoor box. It heats water outside, then pipes that warm water into your home. A split heat pump divides the work between an outdoor unit and an indoor unit called a hydrobox. Refrigerant carries the heat indoors, and the water is heated inside your home.
Winner: Monoblock, for its simpler, all in one design.
Efficiency
Both types reach a seasonal efficiency (SCOP) of around 3.5 to 4.7 when well designed, which means 3.5 to 4.7 units of heat for every unit of electricity. A split can edge ahead where the outdoor unit is far from the house, because refrigerant pipes lose less heat than water pipes over long distances. For most Kent homes, the difference is tiny.
Winner: Draw, with a slight edge to split on long pipe runs.
Cold Weather Performance
Both keep working in temperatures as low as minus 15°C to minus 20°C. Kent’s mild climate rarely tests that, but a monoblock’s outdoor water pipes need antifreeze or frost protection valves to prevent freezing during a power cut in a cold snap. A split has no water outside, so this risk does not exist.
Winner: Split
Unit Cost
A monoblock unit typically costs £3,500 to £7,000. A split system costs £4,000 to £7,500 because you are buying two units, an outdoor unit and an indoor hydrobox.
Winner: Monoblock
Installation Cost
A monoblock usually costs £10,000 to £14,000 fully installed, compared with £11,000 to £16,000 for a split. Split systems need extra refrigerant pipework, an F Gas engineer and more labour. After the £7,500 grant, the gap still remains.
Winner: Monoblock
Running Costs
Running costs are almost identical, at around £850 to £1,300 a year for a typical three bed home in Kent or Sussex. Good design, the right size of unit and a sensible flow temperature matter far more than the type.
Winner: Draw
Reliability
A monoblock’s refrigerant circuit is sealed in the factory, so there are no joints made on site for refrigerant to escape from. A split relies on an engineer making those joints in your home, which adds a small extra risk of leaks over time.
Winner: Monoblock
Indoor Space
A monoblock only needs room indoors for a hot water cylinder and controls. A split also needs a wall mounted indoor unit, roughly the size of a combi boiler. That can be a squeeze in smaller terraced homes in Gillingham, Ramsgate or Hastings.
Winner: Monoblock
Distance From the House
A monoblock works best within a few metres of your home, as warm water loses heat through long outdoor pipes. A split’s refrigerant pipes can often run 30 metres or more, depending on the model. That makes a split handy when the only sensible spot is at the end of a garden or behind an outbuilding.
Winner: Split
Installer Requirements
Any heat pump installer must be MCS certified for you to claim the grant. A split also needs an engineer with F Gas certification, as they will be handling refrigerant. That narrows your choice of installer and adds to the cost.
Winner: Monoblock
Servicing and Maintenance
Both types need an annual service to stay efficient and keep the warranty valid. A monoblock service includes checking the antifreeze or frost valves. A split service includes F Gas leak checks on the refrigerant circuit. Monoblock servicing is usually a little quicker and cheaper.
Winner: Monoblock
Refrigerant
Most new monoblocks use R290 (propane), a natural refrigerant with a global warming potential of just 3. Most split systems use R32, which has a global warming potential of 675. R290 is kept outdoors in a sealed box, so it can be used safely in a monoblock.
Winner: Monoblock
Lifespan
Both types typically last 15 to 20 years or more with regular servicing. Coastal homes in Whitstable, Folkestone or Eastbourne may benefit from a unit with a protective coating against salty air, whichever type you choose.
Winner: Draw
Grant Eligibility
Monoblock and split air source heat pumps both qualify for the £7,500 Boiler Upgrade Scheme grant in England and Wales, as long as an MCS certified installer fits them. Both also benefit from 0% VAT on installation, currently set to run until March 2027.
Winner: Draw
Best Suited Properties
A monoblock suits most detached, semi detached and terraced houses and bungalows with space for the unit near an outside wall. A split suits homes where the outdoor unit must sit far away, properties on exposed sites and some flats. For the typical Kent or South East family home, a monoblock is usually the more practical choice.
Winner: Monoblock, for most homes.
The Overall Winner
The monoblock heat pump wins on most factors. It costs less to install, is simpler, more reliable and uses a greener refrigerant. A split heat pump is the better option when your property’s layout calls for it. A proper survey will show which one your home needs.
Get Expert Advice on Your Air Source Heat Pump Options
Choosing between a monoblock and split air source heat pump depends on your property’s layout, heating requirements and installation preferences. Guscott Heating can help you weigh up the differences with a free estimate, carried out by our MCS certified engineers.
We install air source heat pumps for homeowners and landlords across Kent and the wider South East of England, offering tailored recommendations rather than a one-size-fits-all approach.
Get your free heat pump estimate today and get a recommendation based on your home’s individual heating requirements.
Frequently Asked Questions
Which Brands Make Monoblock and Split Heat Pumps?
Most leading brands make both monoblock and split heat pumps. Mitsubishi Electric offers the Ecodan in both styles, Daikin makes the Altherma 3 M monoblock and Altherma 3 R split, and Samsung sells the EHS Mono and EHS Split. Vaillant’s aroTHERM plus is a popular monoblock, and Vaillant also makes the aroTHERM Split.
Is a Split Heat Pump the Same as Air Conditioning?
A split heat pump is not the same as air conditioning, although it uses similar technology. A split air to water heat pump heats water for your radiators, underfloor heating and taps. A split air conditioner, or air to air heat pump, blows warm or cool air directly into a room and does not qualify for the Boiler Upgrade Scheme.
Do Monoblock Heat Pumps Need a Buffer Tank?
Monoblock heat pumps do not always need a buffer tank. A buffer tank stores a small amount of heated water to stop the heat pump switching on and off too often. Whether you need one depends on how much water your heating system holds and how your radiators are controlled, and the same applies to split systems.
Do You Need Planning Permission for a Monoblock or Split Heat Pump?
You usually do not need planning permission for either type, as most domestic installations in England count as permitted development. The outdoor unit must meet size limits and the MCS 020 noise limit of 42 decibels at a neighbour’s window. Listed buildings, flats and some homes in conservation areas, such as parts of Canterbury and Rye, may need consent.
Can You Swap a Split Heat Pump for a Monoblock Later?
Yes, you can swap a split heat pump for a monoblock later, but it is not a simple like for like change. The refrigerant pipes would be replaced with insulated water pipes and the indoor hydrobox removed or replaced. It usually makes more sense to choose the right type at the start.