Heat Pump Installation in London

Heat Pumps: The Future of Home Heating

With the UK government phasing out gas boilers by 2035 and offering substantial grants for heat pump installation, many London homeowners are considering the switch to this sustainable heating technology. Heat pumps can dramatically reduce carbon emissions and running costs, but they're not suitable for every property.

Hampstead Renovations installs air source and ground source heat pumps across North London. This comprehensive guide covers how heat pumps work, suitability assessment, installation process, costs, grants, and performance in London properties.

How Heat Pumps Work

The Principle

• Extract heat from outside (air or ground)
• Compress refrigerant to increase temperature
• Transfer heat to home's heating and hot water system
• Works like a fridge in reverse
• Efficiency: 3-4 units of heat for every 1 unit of electricity (300-400%)

Types of Heat Pump

Air Source Heat Pump (ASHP)

• Extracts heat from outside air
• Unit mounted on external wall or ground
• Works down to -15°C (most models)
• Most popular choice (easier installation)
• Cost: £8,000-£18,000 installed

Ground Source Heat Pump (GSHP)

• Extracts heat from ground via buried pipes
• More efficient than air source (ground temperature stable)
• Requires garden space (100-200m² typical)
• Higher installation cost but better performance
• Cost: £20,000-£35,000 installed

Is Your Property Suitable?

Ideal Properties

• Well-insulated: EPC rating C or above
• Underfloor heating: Works best with low-temperature systems
• Large radiators: Or willing to upgrade
• Detached/semi-detached: Easier for external unit placement
• Off-gas grid: Replacing oil, LPG, or electric heating
• Garden space: For ground source or outdoor unit

Challenging Properties

• Poor insulation: Heat loss too high (improve first)
• Small radiators: Need upgrading for lower flow temperatures
• Flats: Difficult to site external unit, noise concerns
• Listed buildings: External unit may be refused
• Conservation areas: Additional planning restrictions
• Limited outdoor space: Nowhere for unit or ground loops

Assessment Checklist

1. Insulation: Loft (270mm+), cavity or solid wall insulation
2. Windows: Double-glazed minimum
3. Radiators: Size and type (may need larger)
4. Space: External wall or garden for unit
5. Electrical supply: Adequate for heat pump (upgrade may be needed)
6. Hot water cylinder: Space for new unvented cylinder
7. Planning: Check conservation/listed restrictions

Air Source Heat Pumps (ASHP)

External Unit

• Size: Approx. 1m x 0.8m x 0.8m (fridge-sized)
• Location: External wall or ground mounting
• Clearance: Needs airflow around unit
• Noise: 40-60 dB (similar to fridge hum)
• Distance from neighbours: 1m+ from boundary recommended
• Appearance: Modern unit, visible from street may need planning

Installation Requirements

• Electrical supply: Dedicated circuit from consumer unit
• Hot water cylinder: 200-300L unvented cylinder
• Radiators: May need upgrading to larger sizes
• Pipework: Insulated pipes from outdoor unit
• Condensate drain: Drainage for defrost water

Planning Permission

Usually permitted development if:

• Unit >1m from boundary
• Volume <0.6m³
• Not on front wall (or principal elevation)
• Not above ground floor
• BUT: Conservation areas and listed buildings need permission

Ground Source Heat Pumps (GSHP)

Ground Loop Options

Horizontal Ground Array

• Pipes laid 1-2m deep in trenches
• Requires 100-200m² garden area (2-3x house floor area)
• Garden out of use for 1 year after installation
• Less expensive than vertical

Vertical Boreholes

• Pipes in 50-150m deep boreholes
• Requires minimal garden space
• More efficient (ground temperature stable deeper down)
• Drilling expensive (£5,000-£15,000)

Advantages of GSHP

• More efficient than air source (400-500%)
• Lower running costs
• No visible external unit
• Silent operation (internal unit only)
• Very long lifespan (25+ years for ground loop)

Disadvantages

• High installation cost (£20k-£35k)
• Requires suitable garden space
• Disruptive installation (excavation)
• Geological survey may be needed

Performance and Running Costs

Efficiency (COP - Coefficient of Performance)

• Air source: COP 3.0-3.5 typical (300-350% efficient)
• Ground source: COP 4.0-5.0 typical (400-500% efficient)
• Gas boiler: COP 0.9 typical (90% efficient)
• Meaning: For every 1 kWh of electricity, heat pump produces 3-4 kWh of heat

Annual Running Costs

Example: 3-bed semi-detached house, well-insulated

Current Gas Boiler

• Annual gas usage: 12,000 kWh
• Cost: £1,200 per year (at 10p/kWh)

Air Source Heat Pump

• Annual electricity: 4,000 kWh (12,000 ÷ 3.0 COP)
• Cost: £1,200 per year (at 30p/kWh)
• Savings: Break-even currently, but with grants upfront cost reduced

Ground Source Heat Pump

• Annual electricity: 3,000 kWh (12,000 ÷ 4.0 COP)
• Cost: £900 per year (at 30p/kWh)
• Savings: £300 per year vs gas

Factors Affecting Performance

• Insulation: Better insulation = lower heat demand = lower costs
• Flow temperature: Lower better (underfloor heating ideal at 35-40°C)
• Radiator size: Larger radiators work at lower temperatures
• Winter temperature: ASHP less efficient in very cold weather
• Installation quality: Proper sizing and setup critical

Government Grants and Incentives

Boiler Upgrade Scheme (BUS)

Current government grant (as of 2024):

• Air source heat pump: £7,500 grant
• Ground source heat pump: £7,500 grant
• Biomass boiler: £5,000 grant
• Eligibility: England and Wales, replacing fossil fuel heating
• Property types: Residential, including flats
• Installer: Must be MCS-certified

How to Claim

1. Choose MCS-certified installer
2. Installer applies for grant voucher code
3. Grant deducted from installation cost
4. You pay reduced amount

Example Costs After Grant

• Air source: £14,000 - £7,500 = £6,500
• Ground source: £28,000 - £7,500 = £20,500

Installation Process

Timeline (Air Source Heat Pump)

• Week 1: Survey and design (MCS assessment)
• Week 2-3: Grant application processing
• Week 4: Install external unit and internal components
• Week 5: Commission system, training, certification
• Total: 4-6 weeks from survey to completion

Installation Steps

1. Survey: Heat loss calculation, system design
2. Radiator assessment: Check sizing, upgrade if needed
3. Cylinder installation: New hot water cylinder (if needed)
4. External unit: Mount and connect heat pump
5. Electrical: New circuit, controls, thermostats
6. Pipework: Connect to heating system
7. Commissioning: Test and optimise system
8. Certification: MCS certificate (required for grant)

Living with a Heat Pump

Operating Differences from Gas Boiler

• Lower flow temperature: Radiators warm, not hot to touch
• Constant heating: Best left on low continuously, not on/off
• Slower response: Takes longer to heat up (not instant like gas)
• Hot water: Cylinder heats overnight (cheaper electricity rates)
• Noise: External unit makes gentle humming (40-60 dB)

Optimisation Tips

• Set lower temperature (18-21°C) continuously rather than high intermittently
• Use weather compensation (adjusts output based on outdoor temperature)
• Time hot water heating for cheaper rate periods
• Keep radiators and vents clear
• Regular maintenance (annual service)

Maintenance

Annual Service

• Cost: £150-£300 per year
• Checks: Refrigerant level, electrical connections, filters, safety devices
• Importance: Maintains efficiency and warranty

Lifespan

• Heat pump unit: 15-20 years
• Ground loop (GSHP): 50-100 years
• Warranty: Typically 5-7 years on parts

Challenges and Solutions

Noise Concerns

• Issue: External unit hum (40-60 dB)
• Solution: Position away from bedrooms and neighbours, acoustic barriers
• Quiet models: Premium units <40 dB available

Space Heating in Very Cold Weather

• Issue: ASHP efficiency drops below -5°C
• Solution: Ensure property well-insulated, hybrid systems available (heat pump + gas boiler backup)

Hot Water Demand

• Issue: Heat pumps slower to heat water than gas boilers
• Solution: Larger cylinder (250-300L), timed heating on cheap rate

Cost-Benefit Analysis

Air Source Heat Pump Example

3-bed semi-detached, replacing gas boiler:

• Installation cost: £14,000
• BUS grant: -£7,500
• Net cost: £6,500
• Annual saving: £0-£200 (currently, may improve as electricity greener)
• Carbon saving: 2-3 tonnes CO₂ per year
• Payback: 15-30 years on cost alone, but environmental benefit significant

When Heat Pumps Make Financial Sense

• Replacing oil, LPG, or electric heating (higher savings)
• Building new extension (install from start)
• Property already has underfloor heating
• Combined with solar PV (free electricity for heat pump)
• Off-gas grid properties

Alternatives and Hybrids

Hybrid Heat Pump

• Heat pump + gas boiler
• Heat pump handles most heating, gas boiler for peak demand/hot water
• Lower upfront cost than pure heat pump
• Good transition option
• Cost: £6,000-£10,000 (not eligible for BUS grant)

Hydrogen-Ready Boilers

• New gas boilers can be converted to hydrogen
• Future-proofing option (if hydrogen grid develops)
• Cost similar to standard boiler

Contact Hampstead Renovations