installation

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

How to Prepare Your Home for a Heat Pump: 7-Step UK Guide

First published

TL;DR

  • Insulation first: Loft (270mm) and walls cut heat loss by 35%-saving £300/year on bills (Energy Saving Trust).
  • Radiators matter: Heat pumps need 20-30% more surface area than gas boilers. Use our savings calculator to check yours.
  • Electrical upgrade: Most UK homes need a 20A circuit-check your fuse box before installation.
  • Space requirements: Air-source units need 1m clearance; ground-source loops need 2x your home’s floor area.
  • £7,500 grant: Align your prep with the Boiler Upgrade Scheme to maximise savings.

Heat pumps could cut your heating bills by up to 50% compared to gas boilers-but only if your home is properly prepared. According to OFGEM, 42% of UK households could install a heat pump today, yet many delay due to confusion about insulation, radiators, or electrical requirements. The result? Higher upfront costs, lower efficiency, and missed savings.

This guide covers exactly how to prepare your home for a heat pump, from insulation checks to electrical upgrades and the £7,500 Boiler Upgrade Scheme (BUS) grant. We’ll break down the 7 critical steps, debunk myths (no, you don’t always need new radiators), and show you how to avoid common pitfalls that cost homeowners thousands.

By the end, you’ll know:

  • Whether your current radiators will work (and how to calculate if they’re big enough).
  • How to check if your electrical panel needs an upgrade (most UK homes do).
  • The minimum insulation standards for lofts, walls, and floors.
  • How to align your prep with the BUS grant to maximise your £7,500 discount.
  • What to ask your MCS installer to avoid hidden costs.

Let’s start with the most overlooked step: insulation.

Table of Contents

Is Your Home Truly Heat Pump Ready? A 7-Step Checklist

Before you book an installer, run through this checklist to identify potential issues. Each step includes a "red flag" indicator-if you tick any of these, you’ll need to address them before installation.

StepWhat to CheckRed FlagEstimated Cost to Fix
1. InsulationLoft (270mm), walls, floorsLoft < 100mm or uninsulated walls£300-£1,500
2. RadiatorsSize and output at 45°CSingle-panel radiators or no thermostatic valves£500-£3,000
3. Electrical SystemFuse box, circuit capacityFuse box < 80A or no spare 20A circuit£300-£1,200
4. Outdoor SpaceClearance for ASHP/GSHPNo garden space or noisy neighbours within 1m£0-£500 (relocation)
5. Indoor SpaceHot water cylinder locationNo airing cupboard or space for a 200L cylinder£200-£800
6. EPC RatingEnergy Performance CertificateEPC < D (unless exempt)£0-£500 (retest)
7. BUS Grant EligibilityProperty type, existing systemNon-domestic property or existing heat pumpN/A

Use this table to prioritise your prep work. For example, if your loft insulation is < 100mm, tackle that first-it’ll improve efficiency more than upgrading radiators.

Step 1: The Foundation - Assessing Your Home’s Insulation

Heat pumps work best in well-insulated homes. Why? They operate at lower temperatures than gas boilers (typically 45°C vs. 70°C), so any heat loss forces the system to work harder-reducing efficiency and increasing running costs.

Since May 2024, insulation is no longer mandatory for the Boiler Upgrade Scheme (BUS), but it’s still critical for performance. The Energy Saving Trust estimates that improving insulation can cut heat loss by 35%, saving you £300/year on bills.

Loft Insulation: The 270mm Rule

What to check:

  • Measure the depth of your loft insulation. The UK standard is 270mm of mineral wool or equivalent.
  • Look for gaps, damp, or compressed insulation (which loses effectiveness).

Red flags:

  • Insulation < 100mm (common in homes built before 2000).
  • No insulation in the eaves (where the roof meets the walls).

How to fix it:

  • Top up insulation to 270mm. Cost: £300-£600 for a semi-detached home.
  • Use sheep’s wool or cellulose for eco-friendly options (slightly more expensive but better for moisture control).

Pro tip: If your loft is used for storage, consider insulated loft boards to avoid compressing the insulation.

Wall Insulation: Cavity vs. Solid Walls

What to check:

  • Cavity walls (common in homes built after 1920): Check if they’re already insulated. If not, cavity wall insulation (CWI) can be injected.
  • Solid walls (pre-1920): These require internal or external insulation, which is more expensive but can cut heat loss by 45%.

Red flags:

  • Damp patches on walls (could indicate failed CWI).
  • Single-skin brickwork (solid walls).

How to fix it:

  • Cavity walls: CWI costs £500-£1,500 for a semi-detached home.
  • Solid walls: External insulation costs £8,000-£22,000, but internal insulation is cheaper (£4,000-£13,000).

Pro tip: If you’re eligible for the BUS grant, use the £7,500 to offset insulation costs-it’s a smart way to maximise your investment.

Floor Insulation: The Hidden Heat Thief

What to check:

  • Suspended timber floors: Look for gaps between floorboards or draughts.
  • Solid concrete floors: Check for cold spots (a sign of poor insulation).

Red flags:

  • No insulation under suspended floors.
  • Uninsulated solid floors (common in 1930s-1960s homes).

How to fix it:

  • Suspended floors: Lift floorboards and add 100mm of mineral wool. Cost: £500-£1,500.
  • Solid floors: Add 75mm of rigid insulation before relaying flooring. Cost: £2,000-£6,000.

Pro tip: If you’re replacing flooring, add insulation at the same time-it’s cheaper than retrofitting later.

Step 2: The Heat Distributors - Do You Need Bigger Radiators?

Heat pumps work at lower temperatures than gas boilers, so your radiators need to be 20-30% larger to deliver the same heat output. Many homeowners assume they need to replace all their radiators-but that’s not always true.

How to Calculate Your Radiator Size

Step 1: Find your current radiator output

  • Check the BTU (British Thermal Unit) rating on your radiators. This is usually on a sticker or in the manual.
  • If you can’t find it, measure the radiator’s dimensions and use an online BTU calculator.

Step 2: Adjust for heat pump temperatures

  • Gas boilers typically run at 70°C flow temperature, while heat pumps run at 45°C.
  • Use this formula to adjust the BTU: 
    Adjusted BTU = (Current BTU × 1.3) ÷ (Flow temp ÷ 70)
    Example: A 2,000 BTU radiator at 45°C: 
    Adjusted BTU = (2,000 × 1.3) ÷ (45 ÷ 70) = 4,044 BTU
    This means you’d need a 4,044 BTU radiator to match the output of your current 2,000 BTU radiator at 45°C.

Step 3: Compare to your room’s heat requirement

  • Use a heat loss calculator to find your room’s required BTU.
  • If your adjusted radiator BTU is less than the room’s requirement, you’ll need a larger radiator.

Red flags:

  • Single-panel radiators (common in older homes).
  • No thermostatic radiator valves (TRVs).
  • Radiators that feel lukewarm even when the heating is on.

Alternatives to Replacing Radiators

If your radiators are undersized, you don’t always need to replace them. Try these options first:

  1. Add a second radiator to the same room (e.g., under a window).
  2. Upgrade to double-panel radiators (they have 50% more surface area than single-panel).
  3. Install fan-assisted radiators (they boost heat output by 30%).
  4. Use underfloor heating (UFH) in key rooms (e.g., bathrooms). UFH works well with heat pumps because it operates at low temperatures.

Pro tip: If you’re unsure, ask your MCS installer to perform a heat loss survey. This costs £200-£400 but can save you thousands by identifying exactly which radiators need upgrading.

Step 3: The Powerhouse - Checking Your Electrical System

Heat pumps run on electricity, so your home’s electrical system must be up to the task. Most UK homes built before 2000 will need an upgrade.

Fuse Box and Circuit Requirements

What to check:

  • Fuse box rating: Most heat pumps require a 20A circuit (some larger models need 32A). Check if your fuse box has a spare circuit.
  • Fuse box age: If your fuse box is pre-2000, it may not meet modern safety standards (e.g., no RCD protection).
  • Total load: Heat pumps draw 3-10kW of power. Add this to your existing electrical load (e.g., oven, shower) to ensure your fuse box can handle it.

Red flags:

  • Fuse box < 80A (common in older homes).
  • No spare circuits.
  • Flickering lights when appliances are in use (a sign of overloading).

How to fix it:

  • Upgrade your fuse box to a 100A consumer unit with RCD protection. Cost: £500-£1,200.
  • Add a dedicated 20A circuit for the heat pump. Cost: £300-£800.

Pro tip: If you’re also installing solar panels, upgrade your fuse box now-it’ll save you money later.

Upgrading Your Electrical Panel

If your fuse box is outdated, you may need a full electrical upgrade. Here’s what to expect:

UpgradeWhat It InvolvesCostTime
Fuse box replacementSwap old fuse box for a modern consumer unit£500-£1,2001 day
New circuit for heat pumpAdd a dedicated 20A/32A circuit£300-£8001 day
Full rewireReplace all wiring (rarely needed)£3,000-£10,0001-2 weeks

Pro tip: Ask your installer if they can combine the electrical upgrade with the heat pump installation-some offer discounts for bundling services.

Step 4: The Physical Footprint - Making Space for Your Heat Pump

Heat pumps take up more space than gas boilers, so you’ll need to plan for both indoor and outdoor components.

Air-Source Heat Pumps: Outdoor Unit Placement

Space requirements:

  • 1m clearance around the unit for airflow (check manufacturer specs-some need 1.5m).
  • 3m from bedrooms to minimise noise (heat pumps are quieter than gas boilers but not silent).
  • Flat, stable surface (e.g., concrete slab or paving stones).

Red flags:

  • No outdoor space (e.g., flat with no garden).
  • Neighbours within 1m (could cause noise complaints).
  • Shady or damp location (reduces efficiency).

How to fix it:

  • Relocate the unit to a side passage or roof (if structurally sound). Cost: £500-£1,500.
  • Use a soundproof enclosure (reduces noise by 50%). Cost: £300-£800.

Pro tip: If space is tight, consider a wall-mounted air-source heat pump (e.g., Mitsubishi’s Ecodan Wall-Mounted).

Ground-Source Heat Pumps: Garden or Borehole Space

Space requirements:

  • Horizontal loops: Need 2x your home’s floor area (e.g., 200m² garden for a 100m² home).
  • Vertical boreholes: Need 100-150m depth (requires a drilling rig).

Red flags:

  • Small garden (horizontal loops won’t fit).
  • Rocky soil (increases drilling costs).
  • Shared garden (neighbour permission required).

How to fix it:

  • Opt for boreholes if garden space is limited. Cost: £10,000-£20,000 (vs. £6,000-£12,000 for horizontal loops).
  • Use a hybrid system (ground-source + air-source) to reduce space needs.

Pro tip: If you’re installing a ground-source heat pump, plan for disruption-drilling can take 2-3 days and may damage lawns.

Indoor Space: Where to Put the Cylinder

Heat pumps require a hot water cylinder (typically 200-300L). Most homes replace their old boiler with a cylinder, but you’ll need space for it.

Space requirements:

  • Airing cupboard or utility room (ideal).
  • Minimum 1m² floor space (for a 200L cylinder).
  • Access to plumbing (for connection to the heat pump).

Red flags:

  • No airing cupboard (common in flats).
  • Small kitchen or bathroom (no room for a cylinder).

How to fix it:

  • Use a slimline cylinder (e.g., Gledhill StainlessLite). Cost: £800-£1,500.
  • Install the cylinder in a loft or garage (if insulated). Cost: £200-£500 (for extra plumbing).

Pro tip: If you’re tight on space, consider a combi heat pump (e.g., Daikin Altherma 3 H HT), which doesn’t need a cylinder.

Step 5: The Money - Aligning Your Preparation with the Boiler Upgrade Scheme

The Boiler Upgrade Scheme (BUS) offers £7,500 towards the cost of a heat pump-but only if you meet the eligibility criteria. Here’s how to align your prep work with the grant to maximise savings.

How the BUS Grant Works

Eligibility criteria (as of 2024):

  • Your property must be in England or Wales.
  • You must replace an existing fossil fuel system (gas, oil, or LPG boiler) or an electric storage heater.
  • Your heat pump must be MCS-certified.
  • Your installer must apply for the grant on your behalf.

What the grant covers:

  • £7,500 for air-source or ground-source heat pumps.
  • £5,000 for biomass boilers (not covered in this guide).

What it doesn’t cover:

  • Insulation upgrades.
  • Radiator replacements.
  • Electrical upgrades.

Maximising Your £7,500 Grant

To get the most out of the BUS grant, follow these steps:

  1. Get an EPC certificate (if you don’t have one). The grant requires an EPC no older than 10 years, with no recommendations for loft or cavity wall insulation (unless exempt).

    • Cost: £60-£120.
    • Pro tip: If your EPC recommends insulation, get it done before applying-it’ll improve your heat pump’s efficiency.

  2. Choose an MCS installer who handles the grant application for you. Use our find an installer tool to compare quotes.

    • Pro tip: Ask installers if they offer free EPC assessments-some include this in their quote.

  3. Time your installation to avoid delays. The BUS grant is first-come, first-served, so apply early in the financial year (April-June).

  4. Bundle upgrades to reduce out-of-pocket costs. For example:

    • Use the £7,500 grant to cover the heat pump.
    • Use savings or a 0% interest loan (e.g., Home Energy Scotland) for insulation or radiator upgrades.

Illustrative example:

The Jones family in Manchester replaced their 20-year-old gas boiler with an air-source heat pump. They spent:

  • £12,000 on the heat pump (after £7,500 BUS grant).
  • £1,500 on loft insulation (topped up to 270mm).
  • £2,000 on new radiators for their living room. Total cost: £6,000 (after grant). Their annual heating bill dropped from £1,200 to £600-a 50% saving.

Step 6: The Myths - Debunking Common Heat Pump Misconceptions

Heat pumps are surrounded by myths that deter homeowners. Let’s set the record straight.

Myth 1: “I Need to Replace All My Radiators”

Reality: You might need to replace some radiators, but not all. Use the BTU calculator to check which ones are undersized. In many cases, adding a second radiator or upgrading to double-panel is enough.

Myth 2: “My Electrical System Can’t Handle a Heat Pump”

Reality: Most UK homes can handle a heat pump with a 20A circuit. If your fuse box is outdated, an upgrade costs £500-£1,200-a small price for long-term savings.

Myth 3: “Heat Pumps Don’t Work in Cold Weather”

Reality: Modern heat pumps work efficiently down to -15°C. In fact, Sweden and Norway (where temperatures drop below -20°C) have higher heat pump adoption rates than the UK.

Myth 4: “Heat Pumps Are Noisy”

Reality: Air-source heat pumps are quieter than gas boilers. The average noise level is 40-60 dB (similar to a fridge). Ground-source heat pumps are almost silent.

Myth 5: “I Need Planning Permission”

Reality: Most heat pumps are permitted development in the UK. Exceptions include:

  • Listed buildings.
  • Conservation areas (if the unit is visible from the road).
  • Flats (where the unit would affect neighbours).

Pro tip: Check with your local council or use the GOV.UK planning portal for guidance.

Step 7: The Questions - What to Ask Your MCS Installer

Choosing the right installer is just as important as preparing your home. Use these questions to challenge quotes and avoid hidden costs.

  1. “Can you provide a heat loss survey?”

    • Why ask? This identifies which radiators need upgrading and ensures the heat pump is sized correctly.
    • Red flag: If they say it’s unnecessary.

  2. “What’s the flow temperature of your recommended heat pump?”

    • Why ask? Lower flow temperatures (e.g., 45°C) are more efficient but may require larger radiators.
    • Ideal answer: 45-55°C.

  3. “Will my electrical system need an upgrade?”

    • Why ask? Some installers assume you’ll handle this separately-leading to unexpected costs.
    • Ideal answer: “We’ll check your fuse box and add a dedicated circuit if needed.”

  4. “Do you handle the BUS grant application?”

    • Why ask? Some installers leave this to you, which can delay your grant.
    • Ideal answer: “Yes, we’ll apply on your behalf.”

  5. “What’s your aftercare package?”

    • Why ask? Heat pumps need annual servicing (like gas boilers). Some installers include this in the quote.
    • Ideal answer: “We offer a 5-year warranty and annual servicing for £150/year.”

  6. “Can you provide references from similar properties?”

    • Why ask? Heat pump performance varies by home type (e.g., terraced vs. detached).
    • Red flag: If they can’t provide references.

  7. “What’s the total cost, including extras like insulation or radiators?”

    • Why ask? Some quotes only cover the heat pump, not the full installation.
    • Ideal answer: A detailed breakdown of all costs.

Pro tip: Use our installer comparison tool to check reviews and ratings before committing.

Illustrative Composite: The Smith Family’s Heat Pump Journey

Illustrative composite based on typical UK installations.

The Smiths live in a 1930s semi-detached home in Birmingham. They wanted to replace their 20-year-old gas boiler with a heat pump but were worried about costs and disruption.

Step 1: Insulation Check

  • Loft: 100mm of insulation (needed topping up to 270mm). Cost: £450.
  • Walls: Solid brick (no cavity). They opted for internal wall insulation in the living room. Cost: £3,000.
  • Floors: Suspended timber (no insulation). They added 100mm of mineral wool. Cost: £800.

Step 2: Radiator Assessment

  • Their single-panel radiators were undersized for a heat pump. They replaced 3 radiators (living room, main bedroom, bathroom) with double-panel models. Cost: £1,200.
  • They kept the radiators in the spare bedroom and kitchen (which were already oversized).

Step 3: Electrical Upgrade

  • Their 60A fuse box needed upgrading to 100A. They also added a dedicated 20A circuit for the heat pump. Cost: £900.

Step 4: Space Planning

  • They installed an air-source heat pump on a concrete slab in their side passage (1.5m from the house). Cost: £12,000 (after £7,500 BUS grant).
  • They replaced their old boiler with a 200L hot water cylinder in the airing cupboard. Cost: £1,000.

Total Cost: £11,850 (after grant). Annual Savings: £600 (vs. gas boiler). Payback Period: 12 years (or 8 years with future energy price rises).

The Smiths’ advice:

“Don’t skip the insulation-it made a huge difference to our comfort. And get multiple quotes! Our first installer wanted to replace all our radiators, but the second one showed us we only needed 3.”

FAQ

1. Do I need planning permission for a heat pump?

Most heat pumps are permitted development in the UK, meaning you don’t need planning permission. Exceptions include:

  • Listed buildings (you’ll need listed building consent).
  • Conservation areas (if the unit is visible from the road).
  • Flats (where the unit would affect neighbours). Always check with your local council or use the GOV.UK planning portal.

2. How long does a heat pump installation take?

  • Air-source heat pump: 1-3 days (including outdoor unit and cylinder installation).
  • Ground-source heat pump: 3-5 days (longer if boreholes are needed).
  • Hybrid system: 2-4 days (depends on complexity). Pro tip: Schedule the installation in spring or summer to avoid heating downtime.

3. Can I keep my gas boiler as a backup?

Yes! Hybrid heat pumps combine a heat pump with a gas boiler, switching between the two based on efficiency. This is a good option if:

  • Your home is poorly insulated.
  • You live in a cold climate (e.g., Scottish Highlands).
  • You want peace of mind during extreme weather. Cost: £8,000-£15,000 (after BUS grant).

4. What’s the lifespan of a heat pump?

  • Air-source heat pumps: 15-20 years (with annual servicing).
  • Ground-source heat pumps: 20-25 years (longer lifespan due to stable ground temperatures). Pro tip: Choose a reputable brand (e.g., Mitsubishi, Daikin, Vaillant) and ensure your installer offers a 5-year warranty.

5. How much noise does a heat pump make?

  • Air-source heat pumps: 40-60 dB (similar to a fridge or quiet conversation).
  • Ground-source heat pumps: Almost silent (no outdoor unit). Pro tip: Place the outdoor unit away from bedrooms and use a soundproof enclosure if noise is a concern.

Sources