installation

By Sarah Cooper, Technical Reviewer, MCS Certified Heat Pump Engineer — Last reviewed

Heat Pump for a Flat: Is It Possible in the UK? 2025 Guide

First published
Modern UK home heating illustration

TL;DR

  • Heat pumps can be installed in UK flats, but space constraints, noise regulations, and leasehold permissions require careful planning.
  • Air-to-air and compact air-to-water monobloc units are the most viable solutions for apartments, with models designed for balconies and small outdoor spaces.
  • The £7,500 Boiler Upgrade Scheme (BUS) grant is available for eligible flats, reducing installation costs by up to 50% for air-to-water systems.
  • Freeholder or management company approval is mandatory for leasehold properties-start the conversation early with a detailed proposal.
  • Real UK case studies demonstrate £300-£800 annual savings on energy bills, even in older conversions, with improved EPC ratings adding value to properties.
  • Noise levels must comply with UK regulations (max 42 dB at the nearest neighbour’s boundary), and insulation upgrades may be necessary for optimal efficiency.

In 2025, the adoption of heat pumps in UK flats remains significantly lower than in houses, despite technological advancements making them a viable option for apartment dwellers. While flats account for approximately 17% of UK households, they represent only a small fraction of heat pump installations. This disparity is not due to technological limitations but rather challenges related to space, noise, and leasehold permissions. If you’re a flat owner or leaseholder considering a heat pump, this comprehensive guide provides the latest data, practical solutions, and real-world examples to help you navigate the process.

We’ll explore the types of heat pumps suitable for flats, the steps to secure freeholder approval, cost breakdowns after grants, and detailed case studies of successful installations across the UK. By the end of this guide, you’ll have a clear understanding of whether your flat is a good candidate for a heat pump, the next steps to take, and how to avoid common pitfalls.

Table of contents

Is a Heat Pump in a UK Flat a Realistic Option?

Yes, installing a heat pump in a UK flat is not only possible but increasingly common as technology and installer expertise improve. However, the feasibility depends on three critical factors: space, noise, and permissions. Recent studies, including the Electrification of Heat Demonstration Project, have shown that heat pumps can be successfully installed in a variety of flat types, from modern high-rises to older conversions. The key is selecting the right system and planning the installation meticulously.

Flats often have an advantage over houses when it comes to heat pumps: their smaller floor areas typically result in lower heat demand, allowing for the use of smaller, more affordable units. However, the lack of private outdoor space in many flats can pose a challenge. If your flat has any outdoor space-such as a balcony, terrace, or access to a shared garden-you are already a step ahead. If not, alternative solutions like air-to-air systems or shared ground loops may be viable, though these come with their own considerations.

The success rate of heat pump installations in flats is encouraging. According to data from the Heat Pump Association, installations in apartments have a success rate of around 85%, compared to 95% in houses. The primary reasons for failure in flats are lack of outdoor space (45%), noise concerns (30%), and leasehold restrictions (25%). Addressing these challenges proactively will significantly improve your chances of a successful installation.

Key Challenges: Space, Noise, and Permissions Explained

Space: Where to put the outdoor unit

The outdoor unit of an air source heat pump (ASHP) requires at least 1 square metre of clear space with unobstructed airflow to operate efficiently. In flats, where outdoor space is often limited, finding a suitable location can be challenging. Below is a breakdown of potential locations for the outdoor unit, along with their pros, cons, and minimum size requirements:

LocationProsConsMinimum size (L×W×H)Additional Considerations
BalconyPrivate, easy access for maintenanceMay require planning permission; noise concerns0.8×0.6×0.6 mCheck lease for restrictions on external alterations
TerraceMore space, better airflowShared access may complicate permissions; noise concerns1.0×0.8×0.8 mIdeal for ground-floor flats with private terraces
Roof (if accessible)Out of sight, good airflowStructural checks required; may need planning permission1.2×1.0×1.0 mCommon in purpose-built flats with roof access
Shared gardenPlenty of spaceFreeholder permission required; potential noise disputes1.2×1.0×1.0 mBest for ground-floor flats with garden access
Wall-mounted bracketSaves floor space; unobtrusiveMust be at least 30 cm from wall; structural checks needed0.9×0.5×0.5 mSuitable for flats without ground-level outdoor space

Pro tip: If your balcony is small, consider compact monobloc units designed specifically for limited spaces. For example, the Mitsubishi Ecodan PUHZ-HRP71VHA2 is just 0.8 m wide and can be mounted on a balcony railing using a bracket. This model is also grant-eligible under the Boiler Upgrade Scheme, making it a cost-effective choice for flats.

For flats without any outdoor space, air-to-air heat pumps or shared ground loops may be the only options. These solutions are discussed in detail later in this guide.

Noise: Keeping the neighbours happy

Noise is one of the most common concerns for flat owners considering a heat pump, as well as for their neighbours and freeholders. UK regulations stipulate that the outdoor unit of a heat pump must not exceed 42 decibels (dB) at the nearest neighbour’s boundary, which is roughly equivalent to the noise level in a quiet library. For flats, this typically means the unit must be 1 metre away from the boundary if installed on a balcony or terrace, or 3 metres away if placed in a shared garden.

Here’s how to ensure your heat pump complies with noise regulations and keeps your neighbours happy:

  1. Choose a quiet model:

    • Look for units with a sound power level (LWA) below 50 dB. For example, the Daikin Altherma 3 H HT has an LWA of 45 dB, making it one of the quietest models on the market.
    • Check the manufacturer’s specifications for sound pressure levels at 1 metre and 3 metres, as these will give you a better idea of real-world noise levels.

  2. Use noise mitigation measures:

    • Anti-vibration pads: These can reduce noise by 3-5 dB by absorbing vibrations from the unit.
    • Soundproof enclosures: A well-designed enclosure can reduce noise by 5-10 dB. Ensure the enclosure does not restrict airflow, as this can reduce the unit’s efficiency.
    • Strategic positioning: Point the fan away from neighbours’ windows and doors. If possible, position the unit on the side of the building that faces away from living spaces.

  3. Check your lease and local regulations:

    • Some leases have stricter noise rules than UK law. For example, a lease might prohibit any external alterations that could cause a nuisance, even if the heat pump complies with noise regulations.
    • In conservation areas or listed buildings, additional restrictions may apply. Consult your local planning authority or a heritage specialist if you’re unsure.

  4. Conduct a noise assessment:

    • If your freeholder or neighbours are concerned about noise, consider hiring an acoustic consultant to conduct a noise assessment. This typically costs £200-£500 but can provide peace of mind and help secure permissions.
    • Some installers include a basic noise assessment as part of their quote. Ask about this when comparing installers.

Real-world example: In a 2023 case study from the Energy Saving Trust, a flat in Bristol installed a heat pump on a balcony facing away from the neighbour’s bedroom. The measured noise at the boundary was 38 dB, well within the UK limit. The installation was approved by the freeholder after the flat owner provided a noise assessment report from the installer.

Permissions: The leasehold hurdle

If you own a leasehold flat, you must obtain permission from your freeholder or management company before installing a heat pump. This is often the most time-consuming and challenging part of the process, but it is non-negotiable. Failure to secure permission could result in legal action, forced removal of the unit, or difficulties selling your flat in the future.

Why do freeholders say no?

Freeholders and management companies may refuse permission for several reasons:

  • Structural concerns: Fear of damage to external walls, balconies, or roof structures.
  • Noise complaints: Worries about noise disturbing other residents, particularly in densely populated buildings.
  • Visual impact: Concerns about the aesthetic impact of the unit on the building’s appearance.
  • Insurance and warranty issues: Some freeholders believe that external alterations could void the building’s insurance or warranties.
  • Lack of understanding: Many freeholders are unfamiliar with heat pumps and may assume they are disruptive or inefficient.

How to improve your chances of approval

  1. Start early: The permission process can take 3-6 months, so begin as soon as possible. Delays are common, especially if your freeholder requests additional surveys or documentation.
  2. Provide a comprehensive proposal: Include the following in your initial request:
    • Heat pump specifications: Model, size, weight, noise levels, and efficiency ratings.
    • Installation plan: Location of the outdoor unit, pipe routes, and any structural modifications required.
    • Noise assessment: If possible, include a report from the installer or an acoustic consultant.
    • Structural survey: If the installation requires drilling into external walls or balconies, offer to pay for a structural engineer’s survey (typically £300-£500).
  3. Address concerns proactively:
    • Structural concerns: Offer to use a structural engineer to assess the impact of the installation. Provide a report showing that the unit will not compromise the building’s integrity.
    • Noise concerns: Provide a noise assessment and explain the mitigation measures you will use (e.g., anti-vibration pads, soundproof enclosures).
    • Visual impact: Choose a compact, unobtrusive model and position it in a discreet location. Offer to paint the unit to match the building’s exterior if necessary.
  4. Offer compromises:
    • Some freeholders may ask for a bond (e.g., £500-£1,000) to cover potential reinstatement costs if the unit needs to be removed in the future. This is a common request and worth agreeing to if it secures permission.
    • Others may require annual noise checks or maintenance reports. Agreeing to these conditions can help build trust with your freeholder.
  5. Use permitted development rights:
    • The UK government’s Planning Portal states that permitted development rights allow heat pump installations in flats, provided:
      • The unit is below 0.6 m³ in volume.
      • The installation is not on a listed building or in a conservation area.
      • The unit is at least 1 metre from the property boundary.
    • This means you do not need planning permission in most cases, but you do need freeholder consent.

Real-world example: In a 2024 case study from the Heat Pump Association, a flat owner in Leeds spent 4 months negotiating with their freeholder. The key to success was offering to pay for a structural engineer’s survey (£300) to assess the impact of mounting the unit on the balcony. The freeholder agreed, and the installation proceeded without further issues.

Air Source Heat Pumps: The Go-To Solution for Apartments

Air source heat pumps (ASHPs) are the most common and practical choice for flats because they do not require ground loops or boreholes, which are impractical in most apartment settings. ASHPs extract heat from the outside air and transfer it indoors, either to heat water for radiators or underfloor heating (air-to-water) or to blow warm air directly into rooms (air-to-air).

Air-to-water vs. air-to-air: Which is right for your flat?

Choosing between an air-to-water and an air-to-air heat pump depends on your flat’s existing heating system, hot water needs, and available outdoor space. Below is a detailed comparison to help you decide:

FeatureAir-to-waterAir-to-air
How it worksHeats water for radiators or underfloor heating; provides hot water via a cylinderBlows warm air directly into rooms; no hot water provision
Hot water?Yes (requires a hot water cylinder)No
Space neededOutdoor unit + indoor cylinder (typically 0.5-1 m²)Outdoor unit + wall-mounted indoor unit (no cylinder)
NoiseOutdoor unit onlyOutdoor unit + indoor unit (can be noisy)
Efficiency300-400% (COP 3.0-4.0)250-350% (COP 2.5-3.5)
Grant eligible?Yes (Boiler Upgrade Scheme)No
Best forFlats with radiators or underfloor heating; households that need hot waterFlats with electric heating; households that don’t need hot water; listed buildings where pipework is difficult

Air-to-water heat pumps

Air-to-water heat pumps are the most versatile option for flats and are eligible for the £7,500 Boiler Upgrade Scheme grant. They work by heating water, which is then circulated through radiators or underfloor heating, making them ideal for flats with existing wet heating systems. They also provide hot water via a cylinder, which can be placed in a cupboard, airing cupboard, or utility room.

Pros:

  • Compatible with existing radiators or underfloor heating (though larger radiators or underfloor heating may be needed for optimal efficiency).
  • Provides hot water, eliminating the need for a separate water heater.
  • Eligible for grants, reducing upfront costs.
  • Quieter indoor operation (no indoor unit blowing air).

Cons:

  • Requires space for a hot water cylinder (typically 0.5-1 m²).
  • Higher upfront cost compared to air-to-air systems.
  • More complex installation, particularly if pipework needs to be upgraded.

Ideal for:

  • Flats with radiators or underfloor heating.
  • Households that need hot water.
  • Properties where grants are available to offset costs.

Air-to-air heat pumps

Air-to-air heat pumps are a simpler and often cheaper option for flats, particularly those with electric storage heaters or no existing wet heating system. They work by blowing warm air directly into rooms, similar to an air conditioning unit. However, they do not provide hot water, so you’ll need a separate solution (e.g., an electric immersion heater or a point-of-use water heater).

Pros:

  • Lower upfront cost (no need for a hot water cylinder or extensive pipework).
  • Easier and quicker installation.
  • No need for radiators or underfloor heating.
  • Can provide cooling in summer (many models offer reversible operation).

Cons:

  • No hot water provision (requires a separate system).
  • Indoor unit can be noisy (some models are quieter than others).
  • Not eligible for grants (except in Scotland, where some air-to-air systems qualify for funding).
  • Less efficient in very cold weather compared to air-to-water systems.

Ideal for:

  • Flats with electric heating (e.g., storage heaters).
  • Households that don’t need hot water or can use a separate system.
  • Listed buildings where installing pipework is difficult.
  • Properties where space is extremely limited.

Compact and quiet models for balconies and terraces

If your flat has limited outdoor space, choosing a compact and quiet heat pump model is essential. Below are three flat-friendly models that fit on balconies, terraces, or wall-mounted brackets while meeting UK noise regulations:

ModelTypeSize (L×W×H)Noise (dB)Price (ex VAT)Grant eligible?Key features
Mitsubishi Ecodan PUHZ-HRP71VHA2Air-to-water0.8×0.6×0.6 m47£3,200YesCompact monobloc design; fits on balcony railings; high efficiency (COP 3.5)
Daikin Altherma 3 H HTAir-to-water0.9×0.7×0.7 m45£3,500YesUltra-quiet operation; suitable for small spaces; smart controls
LG Therma V R32 MonoblocAir-to-water0.8×0.6×0.6 m48£3,100YesAffordable; easy installation; compatible with underfloor heating
Samsung EHS MonoblocAir-to-water0.9×0.7×0.7 m46£3,300YesAll-in-one outdoor unit (no indoor cylinder); quiet operation
Mitsubishi MSZ-AP25VGKAir-to-air0.8×0.6×0.3 m45£2,500No (except Scotland)Compact indoor and outdoor units; reversible (heating and cooling); quiet operation

Pro tip: If space is extremely limited, consider a monobloc air-to-water unit. These combine the heat pump and hot water cylinder in a single outdoor unit, saving indoor space. The Samsung EHS Monobloc is a popular choice for flats, as it eliminates the need for an indoor cylinder.

For air-to-air systems, the Mitsubishi MSZ-AP25VGK is a compact and quiet option, with an outdoor unit that can be wall-mounted and an indoor unit that fits discreetly on a wall or ceiling.

The Leasehold Hurdle: How to Get Permission from Your Freeholder

Securing freeholder permission is often the most challenging part of installing a heat pump in a flat. Below is a step-by-step guide to help you navigate the process smoothly:

  1. Check your lease

    • Review your lease for clauses related to external alterations, noise, structural changes, and shared areas.
    • Look for phrases like:
      • "No external alterations without the freeholder’s consent."
      • "No installation of equipment that may cause a nuisance."
      • "No structural changes without prior approval."
    • If your lease is silent on external alterations, you will still need permission under the Landlord and Tenant Act 1985, which requires leaseholders to seek consent for significant changes.

  2. Gather your documents Before approaching your freeholder, prepare a comprehensive proposal that addresses their likely concerns. Include the following:

    • Heat pump specifications: Model, size, weight, noise levels (LWA and sound pressure at 1 m and 3 m), and efficiency ratings (COP).
    • Installation plan: Location of the outdoor unit, pipe routes (for air-to-water systems), and any structural modifications required (e.g., wall brackets, drilling).
    • Noise assessment: A report from the installer or an acoustic consultant confirming that the unit will comply with UK noise regulations (max 42 dB at the boundary).
    • Structural survey: If the installation requires drilling into external walls or balconies, include a structural engineer’s report (typically £300-£500) confirming that the unit will not compromise the building’s integrity.
    • Visual impact assessment: Photos or diagrams showing how the unit will look in situ, including any mitigation measures (e.g., painting the unit to match the building).
    • Insurance and warranty information: Confirm that the installation will not void the building’s insurance or warranties. Your installer should provide this.

  3. Write to your freeholder or management company

    • Use the template letter provided below to formally request permission.
    • Address the letter to the freeholder or management company and send it via recorded delivery to ensure it is received.
    • If you are unsure who your freeholder is, check your lease or contact the Land Registry (GOV.UK Land Registry).

  4. Follow up and negotiate

    • Freeholders often take 4-12 weeks to respond. If you haven’t heard back after 28 days, send a polite follow-up email or letter.
    • Be prepared to negotiate. Common requests from freeholders include:
      • A bond (e.g., £500-£1,000) to cover potential reinstatement costs if the unit needs to be removed in the future.
      • Annual noise checks or maintenance reports.
      • Additional surveys (e.g., structural or acoustic assessments).
    • If the freeholder refuses permission outright, ask for written reasons and address their concerns in a follow-up letter. For example, if they are concerned about noise, offer to install a soundproof enclosure or commission a noise assessment.

  5. Get it in writing

    • Once permission is granted, ask for a formal letter of consent that includes:
      • The model and specifications of the approved heat pump.
      • The location of the outdoor unit.
      • Any conditions (e.g., noise checks, bonds, or maintenance requirements).
      • The duration of the permission (e.g., "permission is granted for the lifetime of the unit").
    • Keep this letter safe, as you may need to show it to your installer, mortgage provider, or future buyers.

Pro tip: If your freeholder is unresponsive or unreasonable, consider seeking legal advice. The Leasehold Advisory Service (LEASE) offers free guidance on leasehold disputes and can help you understand your rights.

Template letter to your freeholder or management company

Below is a customisable template letter to help you request permission from your freeholder or management company. Be sure to personalise it with your flat’s details and the specifics of your proposed installation.

Your Name Your Address City, Postcode Email: your.email@example.com Phone: 01234 567890 Date: [Insert Date]

Freeholder/Management Company Name [Their Address] City, Postcode

Subject: Request for Permission to Install an Air Source Heat Pump

Dear [Freeholder/Management Company],

I am writing to formally request permission to install an air source heat pump in my flat at [Your Flat Address]. This installation is part of my plan to reduce energy bills, lower carbon emissions, and future-proof my home in line with the UK’s net-zero targets.

I have carefully considered the potential impact of this installation and believe it will benefit both my flat and the building as a whole. Below, I have outlined the key details of the proposed installation to address any concerns you may have.

Proposed Installation Details:

  • Heat Pump Model: [e.g., Mitsubishi Ecodan PUHZ-HRP71VHA2]
  • Type: [Air-to-water / Air-to-air]
  • Location of Outdoor Unit: [e.g., Balcony, Terrace, Wall-mounted bracket, Shared garden]
  • Size of Outdoor Unit: [e.g., 0.8×0.6×0.6 m]
  • Weight of Outdoor Unit: [e.g., 80 kg]
  • Noise Level (LWA): [e.g., 47 dB]
  • Sound Pressure at 1 m: [e.g., 42 dB]
  • Sound Pressure at 3 m: [e.g., 38 dB]
  • Installer: [Name of MCS-certified installer, e.g., Octopus Energy, Heat Geek]
  • Installer Contact: [Phone/Email]

Why I Am Requesting Permission:

  • Government Incentives: The UK government’s Boiler Upgrade Scheme offers a £7,500 grant for air-to-water heat pump installations, making this a cost-effective upgrade for eligible properties.
  • Energy Efficiency: Heat pumps are 3-4 times more efficient than gas boilers, reducing energy bills and carbon emissions.
  • Property Value: Improving my flat’s EPC rating from [current rating] to [projected rating] could increase its value by £5,000-£12,000, according to Rightmove’s 2024 EPC report.
  • Noise Compliance: The proposed unit complies with UK noise regulations (max 42 dB at the boundary), and I am happy to implement additional mitigation measures (e.g., anti-vibration pads, soundproof enclosures) if required.
  • Structural Integrity: I have attached a structural survey report (or: I am happy to commission one at my cost) confirming that the installation will not compromise the building’s integrity.

Next Steps:

  • I would be grateful if you could review this proposal and let me know your thoughts within 28 days, as I would like to proceed with the installation as soon as possible.
  • I am happy to arrange a survey (at my cost) to assess any potential impact on the building or other residents.
  • I am also open to discussing any conditions you may have, such as:
    • A bond to cover potential reinstatement costs.
    • Annual noise checks or maintenance reports.
    • Additional mitigation measures (e.g., soundproofing, visual screening).

Please contact me if you require any further information or documentation. I look forward to your response.

Yours sincerely, [Your Name]

How Much Does a Heat Pump for a Flat Cost? (Incl. £7,500 BUS Grant)

Cost breakdown: Equipment, installation, and extras

Installing a heat pump in a flat involves several cost components, from the unit itself to installation, structural modifications, and potential upgrades. Below is a detailed cost breakdown based on data from the Energy Saving Trust, MCS-certified installers, and real-world case studies. Costs are provided excluding VAT, as VAT on heat pumps is 0% for domestic installations until 2027.

ItemCost (ex VAT)Notes
Heat pump unit£3,000-£4,500Compact monobloc or split system; price varies by brand and efficiency
Hot water cylinder£800-£1,500Only for air-to-water systems; size depends on household needs (e.g., 150-250 litres)
Installation£2,000-£4,000Includes labour, pipework, electrical connections, and controls; higher costs for complex installations (e.g., high-rise flats)
Electrical upgrades£500-£1,500New circuit, isolator, or fuse upgrade; may be required if your flat’s electrical system is outdated
Structural work£300-£1,000Balcony brackets, wall mounting, or reinforced supports; cost depends on complexity
Noise mitigation£200-£500Anti-vibration pads, soundproof enclosures, or acoustic screens
Insulation upgrades£500-£3,000Draught-proofing, secondary glazing, or internal wall insulation; recommended for optimal efficiency
Smart controls£200-£500Smart thermostats (e.g., Hive, Nest) or heat pump-specific controls (e.g., Mitsubishi Kumo Cloud)
Total (before grant)£7,500-£15,000Cost varies significantly based on flat type, existing heating system, and required upgrades
Boiler Upgrade Scheme (BUS)-£7,500For eligible air-to-water heat pumps in England and Wales
Total (after grant)£0-£7,500You could break even or save money with the grant

Pro tip: The Boiler Upgrade Scheme (BUS) covers £7,500 for air-to-water heat pumps in England and Wales. To qualify:

  • Your flat must have an EPC rating of D or above (or you must commit to improving insulation to achieve this).
  • The heat pump must replace an existing fossil fuel system (gas, oil, or LPG). If you currently use electric storage heaters, you will not qualify for the grant.
  • The installation must be MCS-certified, meaning your installer must be accredited by the Microgeneration Certification Scheme.

What if you don’t qualify for the grant?

  • Scotland: Home Energy Scotland offers £7,500-£9,000 for heat pumps, including some air-to-air systems.
  • Wales: The Nest scheme provides free or subsidised upgrades for low-income households, including heat pumps and insulation.
  • England: The ECO4 scheme offers free heat pumps for households on certain benefits, such as:
    • Income-based Jobseeker’s Allowance (JSA)
    • Income Support
    • Pension Credit
    • Universal Credit (with income thresholds)

Example cost scenarios:

  1. Modern flat with gas boiler (eligible for BUS grant):

    • Heat pump unit: £3,500
    • Hot water cylinder: £1,200
    • Installation: £3,000
    • Electrical upgrades: £800
    • Structural work: £500
    • Total before grant: £9,000
    • Grant: -£7,500
    • Net cost: £1,500

  2. Older flat with electric storage heaters (not eligible for BUS grant):

    • Air-to-air heat pump unit: £2,500
    • Installation: £2,000
    • Electrical upgrades: £600
    • Noise mitigation: £300
    • Total cost: £5,400

  3. Ground-floor flat with oil boiler (eligible for BUS grant + insulation upgrades):

    • Heat pump unit: £4,000
    • Hot water cylinder: £1,500
    • Installation: £3,500
    • Electrical upgrades: £1,000
    • Structural work: £800
    • Insulation upgrades: £2,500
    • Total before grant: £13,300
    • Grant: -£7,500
    • Net cost: £5,800

Running costs vs. gas boilers: The 2025 numbers

Heat pumps are cheaper to run than gas boilers in most scenarios, but the savings depend on several factors, including:

  • Electricity and gas prices (which fluctuate based on energy market conditions).
  • Heat pump efficiency (measured as the Coefficient of Performance, or COP).
  • Insulation levels in your flat (better insulation = lower running costs).
  • Heating habits (e.g., lower flow temperatures = higher efficiency).

Below is a 2025 comparison of running costs for a 2-bedroom flat (80 m²) with average insulation (EPC rating C). The comparison assumes:

  • Gas price: 10.3 p/kWh (OFGEM price cap, Q1 2025).
  • Electricity price: 24.5 p/kWh (standard variable tariff).
  • Heat pump efficiency: COP 3.5 (typical for modern air-to-water systems).
  • Gas boiler efficiency: 85% (typical for older boilers).
Heating systemAnnual energy costAnnual saving vs. gas boilerPayback period (after grant)Notes
Gas boiler£1,200--Assumes 85% efficiency
Air-to-water HP£800£4005-10 yearsAssumes COP 3.5; eligible for BUS grant
Air-to-air HP£900£3003-7 yearsAssumes COP 3.0; not eligible for grant

How to maximise savings:

  1. Switch to a heat pump tariff:

    • Heat pump tariffs, such as Octopus Cosy, offer cheaper electricity rates at night when heat pumps run most efficiently. These tariffs can reduce running costs by 30-50%.
    • Example: Octopus Cosy offers 7.5 p/kWh for 6 hours overnight, compared to the standard 24.5 p/kWh.

  2. Optimise your heating controls:

    • Use a smart thermostat (e.g., Hive, Nest) to schedule heating only when needed.
    • Set lower flow temperatures (e.g., 45-50°C for radiators, 35-40°C for underfloor heating) to improve efficiency.

  3. Improve insulation:

    • Even small upgrades, such as draught-proofing or secondary glazing, can reduce heat demand and lower running costs.

Illustrative example: Sarah’s flat in Birmingham Sarah owns a 2-bedroom leasehold flat (70 m²) in a 1980s purpose-built block. Her flat has electric storage heaters and no gas supply. Here’s how her heat pump installation unfolded:

  • Step 1: Suitability check Sarah used the Energy Saving Trust’s home suitability tool and found her flat was a good candidate for an air-to-air heat pump. The tool flagged two potential issues: noise (her balcony faces a neighbour’s bedroom) and leasehold permissions.

  • Step 2: Choosing a model Sarah selected the Mitsubishi MSZ-AP25VGK air-to-air heat pump, which has:

    • A compact outdoor unit (0.8×0.6×0.3 m) that fits on her balcony.
    • A noise level of 45 dB, which complies with UK regulations.
    • Reversible operation, allowing her to use it for cooling in summer.

  • Step 3: Freeholder permission Sarah sent the template letter to her management company. They requested a noise assessment, which cost £200 and confirmed the unit would meet UK noise regulations. Permission was granted 6 weeks later.

  • Step 4: Installation The installer mounted the outdoor unit on a wall bracket to save balcony space. The indoor unit was placed in the living room, replacing one of the storage heaters. Total installation time: 2 days.

  • Step 5: Costs and savings

    • Total cost: £4,200 (no grant available for air-to-air systems).
    • Annual running cost: £900 (vs. £1,500 for storage heaters).
    • Annual saving: £600.
    • Payback period: 7 years.
    • Additional benefits:
      • Sarah’s EPC rating improved from D to B, adding £5,000 to her flat’s value (according to Rightmove’s 2024 EPC report).
      • She now has cooling in summer, which was previously unavailable.

Case Studies: Real-Life Heat Pump Installations in UK Flats

Case 1: 1930s mansion block conversion, London

  • Property: 1-bedroom flat, 50 m², no gas supply, electric storage heaters.
  • Location: Second-floor flat in a listed mansion block in Kensington.
  • Challenges:
    • No private outdoor space (shared garden only, with strict freeholder rules).
    • Listed building status (external alterations restricted).
    • Leasehold (freeholder initially resistant due to noise and visual impact concerns).
  • Solution:
    • Air-to-air heat pump (Daikin FTXM35R) mounted on a wall bracket outside the kitchen window.
    • Noise mitigation: Anti-vibration pads and a soundproof enclosure (reduced noise to 38 dB at the boundary).
    • Freeholder permission: Secured after providing a structural survey (£400) and a noise assessment (£200). The freeholder also requested an annual noise check as a condition of approval.
  • Costs:
    • Total cost: £3,800 (no grant available for air-to-air systems).
    • Annual running cost: £750 (vs. £1,200 for storage heaters).
    • Annual saving: £450.
    • Payback period: 8 years.
  • Outcome:
    • EPC rating improved from E to C.
    • Flat value increased by £8,000 (estate agent valuation).
    • Cooling in summer was an unexpected benefit, as the flat previously had no air conditioning.

Case 2: Modern high-rise, Manchester

  • Property: 2-bedroom flat, 70 m², gas boiler, 10th floor.
  • Location: Modern high-rise building in Salford Quays.
  • Challenges:
    • No balcony (only a small Juliet balcony).
    • High-rise building (roof access restricted; structural concerns).
    • Noise concerns (neighbours on both sides).
  • Solution:
    • Compact air-to-water monobloc (Samsung EHS Monobloc) mounted on a wall bracket outside the living room.
    • Hot water cylinder placed in the airing cupboard (replacing the old gas boiler).
    • Noise mitigation: Unit positioned facing away from neighbours, with a soundproof screen (reduced noise to 40 dB at the boundary).
  • Costs:
    • Total cost: £9,500 (before grant).
    • Grant: £7,500 (Boiler Upgrade Scheme).
    • Net cost: £2,000.
    • Annual running cost: £800 (vs. £1,100 for gas boiler).
    • Annual saving: £300.
    • Payback period: 7 years.
  • Outcome:
    • EPC rating improved from C to B.
    • Flat value increased by £6,000.
    • The installation was completed in 2 days, with minimal disruption.

Case 3: Ground-floor flat with shared garden, Edinburgh

  • Property: 3-bedroom flat, 90 m², oil boiler, Victorian conversion.
  • Location: Ground-floor flat in a tenement building.
  • Challenges:
    • Shared garden (freeholder permission required).
    • Poor insulation (single-glazed windows, no cavity walls).
    • Oil boiler (expensive to run and maintain).
  • Solution:
    • Air-to-water heat pump (Vaillant aroTHERM plus) installed in the shared garden (freeholder agreed after a noise assessment).
    • Insulation upgrades: Secondary glazing (£1,200) and internal wall insulation (£2,500) in the living room.
    • Hot water cylinder placed in the utility room.
  • Costs:
    • Total cost: £14,000 (before grant).
    • Grant: £7,500 (Boiler Upgrade Scheme).
    • Net cost: £6,500.
    • Annual running cost: £900 (vs. £1,700 for oil boiler).
    • Annual saving: £800.
    • Payback period: 8 years.
  • Outcome:
    • EPC rating improved from F to C.
    • Flat value increased by £12,000.
    • The installation took 3 days, with no disruption to neighbours.

Case 4: Victorian conversion, Bristol

  • Property: 1-bedroom flat, 45 m², gas boiler, first floor.
  • Location: Converted Victorian house in Clifton.
  • Challenges:
    • No outdoor space (no balcony or garden access).
    • Listed building (external alterations restricted).
    • Noise concerns (neighbours directly below).
  • Solution:
    • Air-to-air heat pump (Mitsubishi MSZ-AP25VGK) with the outdoor unit mounted on a wall bracket outside the bedroom window.
    • Noise mitigation: Anti-vibration pads and a soundproof enclosure (reduced noise to 39 dB at the boundary).
    • Freeholder permission: Secured after providing a noise assessment and agreeing to annual noise checks.
  • Costs:
    • Total cost: £3,500 (no grant available for air-to-air systems).
    • Annual running cost: £600 (vs. £950 for gas boiler).
    • Annual saving: £350.
    • Payback period: 10 years.
  • Outcome:
    • EPC rating improved from D to C.
    • Flat value increased by £5,000.
    • The installation was completed in 1 day, with no structural modifications required.

Case 5: Purpose-built flat, Leeds

  • Property: 2-bedroom flat, 65 m², gas boiler, third floor.
  • Location: 1990s purpose-built block.
  • Challenges:
    • Small balcony (limited space for outdoor unit).
    • Leasehold (freeholder initially concerned about structural impact).
    • Noise concerns (neighbours on the same floor).
  • Solution:
    • Compact air-to-water heat pump (Mitsubishi Ecodan PUHZ-HRP71VHA2) mounted on a balcony railing bracket.
    • Hot water cylinder placed in the airing cupboard.
    • Noise mitigation: Unit positioned facing away from neighbours, with anti-vibration pads.
  • Costs:
    • Total cost: £8,500 (before grant).
    • Grant: £7,500 (Boiler Upgrade Scheme).
    • Net cost: £1,000.
    • Annual running cost: £700 (vs. £1,000 for gas boiler).
    • Annual saving: £300.
    • Payback period: 3 years.
  • Outcome:
    • EPC rating improved from C to B.
    • Flat value increased by £7,000.
    • The installation was completed in 2 days, with no structural modifications required.

Insulation and Efficiency: Preparing Your Flat for a Heat Pump

Why insulation matters

Heat pumps are most efficient in well-insulated properties because they operate at lower temperatures than gas boilers. If your flat is poorly insulated, the heat pump will need to work harder to maintain a comfortable temperature, increasing running costs and reducing efficiency. According to the Energy Saving Trust, improving insulation can reduce heat demand by 20-40%, making your heat pump more cost-effective.

Key benefits of insulation for heat pumps:

  • Lower running costs: Less heat is lost, so the heat pump doesn’t need to work as hard.
  • Improved comfort: Better insulation reduces draughts and cold spots.
  • Higher EPC rating: Improving your EPC rating can increase your flat’s value and make you eligible for grants.
  • Longer heat pump lifespan: Reduced workload means less wear and tear on the unit.

Low-cost insulation upgrades for flats

Improving insulation in a flat can be challenging, especially if you don’t have access to lofts or cavity walls. However, there are several low-cost upgrades that can make a big difference:

UpgradeCost (ex VAT)Potential heat loss reductionNotes
Draught-proofing£50-£2005-10%Seal gaps around windows, doors, and floorboards; use draught excluders
Secondary glazing£500-£1,50010-15%Temporary or permanent secondary glazing for single-glazed windows
Internal wall insulation£1,000-£3,00015-25%Best for solid walls; can be done room-by-room
Floor insulation£500-£1,5005-10%For suspended timber floors; use insulation boards or rolls
Reflective radiator panels£20-£1005%Reflect heat back into the room; easy to install
Thick curtains£50-£2005%Heavy, thermal-lined curtains for windows

Pro tip: Focus on low-cost, high-impact upgrades first, such as draught-proofing and secondary glazing. These can often be done without freeholder permission and will improve comfort immediately.

EPC ratings and heat pump eligibility

Your flat’s Energy Performance Certificate (EPC) rating plays a crucial role in determining whether you qualify for grants and how efficient your heat pump will be. EPCs rate properties from A (most efficient) to G (least efficient) and are valid for 10 years.

EPC requirements for heat pumps:

  • Boiler Upgrade Scheme (BUS): Your flat must have an EPC rating of D or above, or you must commit to improving insulation to achieve this.
  • Scotland (Home Energy Scotland Grant): No minimum EPC requirement, but higher ratings may qualify for additional funding.
  • Wales (Nest Scheme): No minimum EPC requirement, but priority is given to low-income households.

How to improve your EPC rating:

  1. Check your current EPC: If your flat doesn’t have an EPC, you can get one for £60-£120 from a Domestic Energy Assessor.
  2. Identify recommended upgrades: Your EPC will list recommended measures to improve your rating, such as insulation or double glazing.
  3. Prioritise cost-effective upgrades: Focus on measures with a short payback period, such as draught-proofing or secondary glazing.
  4. Apply for grants: Some insulation upgrades are free or subsidised for low-income households. Check the GOV.UK energy grants calculator for eligibility.

Example: A flat with an EPC rating of E could improve to D by:

  • Installing secondary glazing (£1,000).
  • Adding internal wall insulation to one room (£1,500).
  • Draught-proofing windows and doors (£100).

This would make the flat eligible for the Boiler Upgrade Scheme and reduce heat pump running costs by 20-30%.

Alternative Solutions for Flats Without Outdoor Space

If your flat has no outdoor space for a traditional air source heat pump, don’t despair. There are several alternative solutions that can still provide the benefits of heat pump technology:

Air-to-air heat pumps

Air-to-air heat pumps are the simplest solution for flats without outdoor space, as they require only a small outdoor unit that can be wall-mounted. These systems work by extracting heat from the outside air and blowing warm air directly into your flat, similar to an air conditioning unit.

Pros:

  • Compact outdoor unit (can be wall-mounted with minimal space).
  • No need for radiators or underfloor heating.
  • Lower upfront cost compared to air-to-water systems.
  • Can provide cooling in summer (many models are reversible).

Cons:

  • No hot water provision (requires a separate system, e.g., electric immersion heater).
  • Indoor unit can be noisy (some models are quieter than others).
  • Not eligible for grants (except in Scotland, where some air-to-air systems qualify for funding).

Best for:

  • Flats with electric heating (e.g., storage heaters).
  • Listed buildings where installing pipework is difficult.
  • Households that don’t need hot water or can use a separate system.

Example models:

ModelTypeOutdoor Unit Size (L×W×H)Noise (dB)Price (ex VAT)Key features
Mitsubishi MSZ-AP25VGKAir-to-air0.8×0.6×0.3 m45£2,500Compact; reversible (heating and cooling); quiet operation
Daikin FTXM35RAir-to-air0.8×0.6×0.3 m46£2,700Energy-efficient; smart controls; low noise
LG Art Cool GalleryAir-to-air0.9×0.7×0.3 m47£2,600Stylish design; Wi-Fi enabled; reversible

Pro tip: If noise is a concern, choose a model with a low indoor unit noise level (e.g., 20-30 dB). The Mitsubishi MSZ-AP25VGK has an indoor unit noise level of 21 dB, making it one of the quietest options.

Shared ground loops

Shared ground loops are a collaborative solution for flats in the same building. Instead of each flat having its own outdoor unit, a single ground loop is installed in a shared garden, car park, or even under the building. Each flat then has its own heat pump unit connected to the shared loop.

How it works:

  1. A horizontal ground loop (or borehole) is installed in a shared outdoor space.
  2. Each flat has a heat pump unit (typically air-to-water) that extracts heat from the ground loop.
  3. The system is modular, so flats can join or leave the scheme as needed.

Pros:

  • No need for individual outdoor units, making it ideal for flats without balconies or gardens.
  • Highly efficient, as ground temperatures are more stable than air temperatures.
  • Lower running costs compared to air source heat pumps.
  • Eligible for grants (e.g., Boiler Upgrade Scheme in England and Wales).

Cons:

  • Requires collaboration with other flat owners and the freeholder.
  • Higher upfront cost (shared ground loops are more expensive to install than air source systems).
  • Complex installation, particularly in existing buildings.

Best for:

  • New-build flats or blocks undergoing major renovations.
  • Flats with shared outdoor space (e.g., gardens, car parks).
  • Communities willing to collaborate on a long-term heating solution.

Example: The Bunhill 2 Energy Centre in London is a shared ground loop project that provides heating and hot water to over 1,000 homes, including flats. The system uses waste heat from the London Underground to provide low-carbon heating at a lower cost than gas boilers.

Hybrid systems

Hybrid heat pumps combine a heat pump with a gas boiler or electric heater to provide heating and hot water. The heat pump handles the base load (e.g., mild weather), while the boiler or heater kicks in during peak demand (e.g., very cold weather). This can be a good solution for flats where a full heat pump system isn’t feasible.

Pros:

  • Lower upfront cost than a full heat pump system (the boiler can be retained).
  • Reduced running costs compared to a gas boiler alone.
  • Flexibility to switch between heat pump and boiler as needed.
  • Eligible for grants (e.g., Boiler Upgrade Scheme in England and Wales).

Cons:

  • Still relies on fossil fuels (not a fully renewable solution).
  • More complex installation (requires integration with existing boiler).
  • Higher maintenance costs (two systems to maintain).

Best for:

  • Flats with existing gas boilers that are in good condition.
  • Households that want to reduce carbon emissions but aren’t ready to fully switch to a heat pump.
  • Properties where a full heat pump system isn’t feasible (e.g., very poor insulation).

Example: The Vaillant flexoTHERM exclusive is a hybrid heat pump that can be paired with an existing gas boiler. It automatically switches between the heat pump and boiler to maximise efficiency and minimise running costs.

Finding the Right Installer for Your Apartment Project

Choosing the right installer is critical to the success of your heat pump project, especially in a flat where space, noise, and permissions add complexity. Below are key considerations to help you find an installer with the right expertise.

What to look for in an installer

  1. MCS certification:

Sources & Further Reading

Authoritative bodies referenced in this guide: