Thinking about replacing a gas boiler with a heat pump? This guide explains how installers normally build a price, what affects the total, how to estimate running costs yourself and how to get reliable quotes in the UK. It avoids one-size-fits-all figures and gives the steps you need to produce accurate, current cost estimates for your home.
Key takeaways
- Two main types: air-source (easier to install) and ground-source (more efficient but needs groundworks). Choose by space, budget and insulation.
- Upfront costs vary widely. Equipment, installer labour, any radiator or cylinder upgrades and groundworks are the biggest items.
- Running cost depends on your home’s annual heat demand, the heat pump’s coefficient of performance (COP) and local electricity and gas prices — use the simple formulas below to estimate.
- Check current government support, VAT rules and local grants before budgeting — these change and can cut the effective cost significantly.
- Get at least three detailed quotes from accredited installers, and ask for a heat-loss calculation, estimated running costs and details of warranties and maintenance.
Air-source versus ground-source: installation differences
Air-source heat pumps (ASHPs) extract heat from outside air. They need an outdoor unit and a compatible indoor system (wet radiators, underfloor heating or fan coils). ASHPs are usually quicker to install and need less disruption.
Ground-source heat pumps (GSHPs) use buried pipes to gather heat from the ground. They are typically more efficient but require drilling or excavation for horizontal loops or boreholes — this adds significant groundworks and planning considerations.
How installers build a price
Installers combine several cost elements into a single quote. Ask each installer to break their quote down by these items so you can compare like for like:
- Heat pump equipment: indoor and outdoor units, controls and any required cylinders. Higher-quality models and larger capacity units cost more.
- Installation labour: time on site for fitting, commissioning and testing. Complex homes (multi-storey, many radiators) will need more labour.
- Distribution upgrades: converting an existing radiator system to run at lower temperatures may need larger radiators or new underfloor heating and a suitable hot-water cylinder.
- Electrical work: many heat pumps need an upgraded consumer unit or a dedicated electrical supply.
- Groundworks (GSHP only): trenching or drilling for loops, plus reinstatement of landscaping.
- Controls and commissioning: smart thermostats, weather compensation and proper commissioning to achieve rated efficiency.
- Removal and disposal: removing an old boiler and flues.
- Optional work: loft or wall insulation, draught-proofing and other efficiency improvements.
Estimate running costs yourself
Use these simple formulas to estimate annual running costs so you can compare apples with apples.
To estimate heat-pump annual electricity cost:
Annual heating demand (kWh) ÷ average seasonal COP = electrical kWh used
Electrical kWh used × your electricity price (p/kWh) = annual heating cost
To estimate a gas-boiler equivalent:
Annual heating demand (kWh) ÷ boiler efficiency = gas kWh required
Gas kWh required × your gas price (p/kWh) = annual boiler heating cost
Notes:
- Annual heating demand is the energy your home needs for space heating and hot water. You can get this from an existing energy bill history, an EPC or a heat-loss assessment.
- Seasonal COP is the average real-world efficiency of the heat pump across the heating season; it will be lower than the maximum quoted COP. Ask installers for their expected seasonal COP for your property.
- Include any electricity for backup heaters, pumps or fans when you estimate usage.
What most affects the total cost
- Property size and heat demand: larger homes require higher-capacity systems and more distribution work.
- Existing heating system: if radiators are undersized you may need replacements or underfloor heating.
- Groundworks: GSHP excavation or boreholes are the biggest single variable item.
- Insulation and fabric quality: poorly insulated homes need larger systems and will run less efficiently — fabric improvements can reduce long-term costs.
- Access and complexity: hard-to-reach sites, listed buildings or complex plumbing increase labour hours.
- Electrical supply: homes with limited mains capacity may need an upgrade, which adds cost and lead time.
How to get accurate quotes
Follow this checklist when requesting quotes so you can compare fairly.
- Ask for a written heat-loss calculation and the proposed system size in kW.
- Request the expected seasonal COP and an estimated annual running-cost calculation using your current energy prices.
- Get a fully itemised quote: equipment, labour, groundworks, electrical upgrades, cylinder/radiator work and VAT broken out.
- Check installer credentials: ask for accreditation (such as recognised industry schemes), previous job references and examples of similar installations.
- Confirm what warranties and aftercare are included and the cost of optional annual servicing.
- Ask about lead times and availability for parts and ongoing support.
Payback and finance — how to judge affordability
Payback is the time it takes for energy bill savings to cover the extra upfront cost compared with a like-for-like gas boiler replacement. Calculate payback by dividing the additional upfront cost by the expected annual saving. Be cautious: payback depends on future energy prices, maintenance costs and behavioural changes.
Common ways to make a heat pump more affordable:
- Check current government and local authority incentives and any reduced VAT treatments.
- Consider targeted measures first: improve insulation and draught-proofing to reduce required system size.
- Explore green loans, energy-efficient mortgages or retrofit finance options offered by banks or specialist lenders.
Deciding if a heat pump is right for your home
Heat pumps work best where: heat demand is moderate, the property has good insulation, and the distribution system can run at lower flow temperatures. GSHPs can be very efficient, but the installation disruption and site suitability must be weighed against long-term running savings. ASHPs are generally the simpler swap for many UK homes.
Key questions to ask an installer
- What exact model and capacity are you proposing, and why?
- What seasonal COP do you expect for my home and how did you calculate it?
- Will I need radiator upgrades, a new cylinder or electrical work?
- Is groundworks required, and how will the site be reinstated?
- What warranties are offered and what does routine servicing cost?
FAQs
How long does installation usually take?
Times vary by system complexity. ASHP retrofits can sometimes be completed in a few days; installations requiring extensive radiator changes, cylinders or groundworks will take longer. Ask installers for a realistic programme for your site.
Will I need planning permission?
Most domestic heat pumps do not require full planning permission, but there are exceptions for listed buildings, conservation areas or large groundworks for GSHPs. Check local planning authority guidance before consenting to work.
Do heat pumps need backup heating?
Some homes keep a small electric boost or use a hybrid system combining a heat pump with a gas boiler. Whether you need backup depends on your system design and how low external temperatures affect performance.
How reliable are installer quotes I find online?
Online estimates can give a rough idea but are rarely accurate for your property. Always get a site survey and a detailed written quote.
Where can I find up-to-date financial support and rules?
Government support, VAT rules and local schemes change regularly. Check official UK government sources, Citizens Advice or trusted energy-advice organisations for current schemes and eligibility rules.
Next steps: collect recent energy bills, request an EPC or a heat-loss assessment, then ask three accredited installers for fully itemised quotes. Keep a close eye on current incentives and VAT guidance before you finalise your decision.
About this article
This article is for general information and educational purposes only and is not financial advice. Prices, rules and personal circumstances can change, so check official sources or seek qualified advice before making important financial decisions.
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