--- title: "Radiators for Air Source Heat Pumps: Sizing Guide" description: "Do you need new radiators for an air source heat pump? Our sizing guide covers operating temperatures, BTU output, upgrade costs and radiator compatibility for UK homes." lang: en-GB json-ld: | [ { "@context": "https://schema.org", "@type": "LocalBusiness", "name": "Greentech Renewables", "image": "https://www.greentechrenewables.co.uk/logo.png", "description": "MCS Certified Solar Panel and Battery Storage Installers in Greater Manchester. Trusted by 2000+ UK homeowners for renewable energy solutions.", "address": { "@type": "PostalAddress", "addressLocality": "Greater Manchester", "addressCountry": "GB" }, "telephone": "0333 577 7010", "email": "admin@greentechrenewables.co.uk", "url": "https://www.greentechrenewables.co.uk", "priceRange": "££", "aggregateRating": { "@type": "AggregateRating", "ratingValue": "4.9", "reviewCount": "105" }, "sameAs": [ "https://www.facebook.com/greentechrenewables", "https://www.instagram.com/greentechrenewables" ], "hasOfferCatalog": { "@type": "OfferCatalog", "name": "Renewable Energy Services", "itemListElement": [ { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Solar Panel Installation" } }, { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Battery Storage Systems" } }, { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Air Source Heat Pumps" } } ] } }, { "@context": "https://schema.org", "@graph": [ { "@type": [ "LocalBusiness", "HVACContractor" ], "@id": "https://www.greentechrenewables.co.uk/#business", "name": "Greentech Renewables", "url": "https://www.greentechrenewables.co.uk", "telephone": "0333 577 7010", "address": { "@type": "PostalAddress", "addressLocality": "Manchester", "addressRegion": "Greater Manchester", "addressCountry": "GB" }, "areaServed": "Greater Manchester", "hasCredential": "MCS Certified" }, { "@type": "Article", "@id": "https://www.greentechrenewables.co.uk/ashp/radiators-for-heat-pumps#article", "headline": "Radiators for Air Source Heat Pumps: Sizing Guide & Compatibility", "description": "Do you need new radiators for an air source heat pump? Our sizing guide covers operating temperatures, BTU output, upgrade costs and radiator compatibility for UK homes.", "url": "https://www.greentechrenewables.co.uk/ashp/radiators-for-heat-pumps", "author": { "@type": "Organization", "name": "Greentech Renewables" }, "publisher": { "@type": "Organization", "name": "Greentech Renewables", "logo": { "@type": "ImageObject", "url": "https://www.greentechrenewables.co.uk/logo.png" } }, "mainEntityOfPage": "https://www.greentechrenewables.co.uk/ashp/radiators-for-heat-pumps" }, { "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "Do I definitely need new radiators for a heat pump?", "acceptedAnswer": { "@type": "Answer", "text": "Not necessarily. Many modern homes with double-panel radiators only need upgrades in one or two rooms. A heat loss survey will tell you exactly which rooms are undersized before any money is spent." } }, { "@type": "Question", "name": "Will my existing radiators work at all with a heat pump?", "acceptedAnswer": { "@type": "Answer", "text": "Yes, but they may not heat rooms adequately on the coldest days. A well-designed system with correctly sized radiators will be comfortable all year. Undersized radiators mean the heat pump has to work harder and run at higher (less efficient) temperatures." } }, { "@type": "Question", "name": "Can I keep my existing radiators and just accept slightly lower room temperatures?", "acceptedAnswer": { "@type": "Answer", "text": "Some homeowners choose to do this, especially in rooms they rarely use. Your installer can set different temperature zones. However, in main living areas this is usually a poor compromise — it's better to size the radiators correctly." } }, { "@type": "Question", "name": "Is underfloor heating better than radiators for heat pumps?", "acceptedAnswer": { "@type": "Answer", "text": "Underfloor heating (UFH) is ideal for heat pumps because it operates at even lower flow temperatures (30–40°C vs 45–55°C for radiators), which maximises heat pump efficiency. However, fitting UFH in existing rooms is expensive and disruptive. For most retrofit installations, upgrading radiators is the more practical approach." } }, { "@type": "Question", "name": "How long does a radiator upgrade take?", "acceptedAnswer": { "@type": "Answer", "text": "A single radiator swap takes 1–2 hours. A full-house upgrade of 4–6 radiators would typically be done as part of the heat pump installation — usually within the same 2–3 day installation window." } }, { "@type": "Question", "name": "Will the £7,500 Boiler Upgrade Scheme grant cover radiator costs?", "acceptedAnswer": { "@type": "Answer", "text": "The BUS grant of £7,500 applies to the heat pump installation itself. Radiator upgrades are typically included within the overall installation quote — a reputable installer will bundle them together. The grant is paid directly to the installer and reduces your net cost accordingly." } } ] } ] } ] --- [0333 577 7010 ](tel:03335777010)[admin@greentechrenewables.co.uk ](mailto:admin@greentechrenewables.co.uk) ★ 4.9 on Trustpilot [![Greentech Renewables - MCS Certified Solar Installers](/assets/greentech-logo-DICMm454.jpg)](/) [Home](/) Our Services Solar Energy [ Residential Solar Home solar panel systems ](/solar-panels)[ Commercial Solar Business & industrial solutions ](/commercial-solar)[ Price Estimator Get an instant quote ](/solar-estimator) Energy Storage [ Battery Storage Store excess solar energy ](/battery-storage) Heat Pumps [ Air Source Heat Pumps Efficient home heating ](/heat-pumps)[ Octopus Cosy Installer Accredited Cosy fitting in Manchester ](/octopus-cosy-heat-pump-installer-manchester)[ Boiler Upgrade Scheme £7,500–£9,000 government grant ](/boiler-upgrade-scheme-bus) EV Charging [ Home EV Chargers Charge at home ](/ev-charging)[ Commercial Charging Workplace solutions ](/ev-charging#commercial) Ready to switch to renewable energy? 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You may get free panels [Check Eligibility](/grants/warm-homes-plan-eligibility) [Case Studies](/case-studies) [0% Finance](/finance)[Quick Solar Price](/solar-estimator) # Radiators for Air Source Heat Pumps: Do You Need to Upgrade? Most homes need some changes, but very few need a full house swap. This guide explains how heat pump radiators work, how to size them correctly, and what it costs to upgrade. [Get Free Heat Pump Survey](/free-quote) [0333 577 7010](tel:03335777010) ## Why Heat Pump Radiators Work Differently A gas boiler heats water to 70–80°C and pumps it through your radiators quickly. Heat pumps operate at much lower flow temperatures — typically 35–55°C — and run for longer periods throughout the day. This lower flow temperature is actually more efficient and cheaper to run, but it means radiators need to emit the same amount of heat at a lower temperature. To do that, they need more surface area. Learn more about [how air source heat pumps work](/ashp/how-do-heat-pumps-work). System Flow Temperature Gas boiler 70–80°C Modern condensing boiler 55–65°C Air source heat pump (standard) 45–55°C Air source heat pump (low-temp optimised) 35–45°C Underfloor heating 30–40°C A radiator that was perfectly sized for a boiler running at 75°C may only emit 50–60% of that heat output when connected to a heat pump running at 45°C. That shortfall has to be made up somewhere. ## How to Tell If Your Radiators Are Adequate Before installing a heat pump, a good installer will carry out a room-by-room heat loss survey. This calculates how much heat (in kW or BTU) each room needs to maintain a comfortable temperature on the coldest day of the year. Your radiators are adequate if their rated output at the heat pump's flow temperature meets or exceeds each room's heat loss. Most radiator manufacturers publish 'correction factor' tables to help you calculate this. ### The Correction Factor Calculation Radiator output ratings are based on a standard ΔT of 50°C (mean water temperature of 70°C, room at 20°C). At lower heat pump temperatures the correction factor drops significantly: Flow Temp (°C) Mean Water Temp (°C) Correction Factor 70 65 1.00 (rated output) 60 55 0.77 50 45 0.55 45 40 0.46 40 35 0.38 35 30 0.30 **Example:** A 2kW radiator rated at ΔT50 will only output **0.92kW** at a 45°C heat pump flow temperature (2kW × 0.46). If the room heat loss is 1.2kW, that radiator is undersized and will need upgrading. ## Room-by-Room Radiator Sizing Guide These figures are approximate guides for a well-insulated UK semi-detached home. Your actual heat loss will vary by insulation level, ceiling height, window size, and the number of external walls. Room Typical Heat Loss Recommended Output at 45°C Typical Size Small bedroom 0.5–0.7 kW 1.2–1.5 kW rated 600 × 600mm double panel Double bedroom 0.7–1.0 kW 1.6–2.2 kW rated 600 × 900mm double panel Master bedroom 0.8–1.2 kW 1.8–2.6 kW rated 600 × 1000mm double panel Living room 1.2–1.8 kW 2.7–4.0 kW rated 600 × 1400mm double panel Open-plan kitchen/diner 1.5–2.5 kW 3.3–5.5 kW rated Multiple radiators or UFH Bathroom 0.4–0.6 kW 0.9–1.3 kW rated Towel rail + panel Hallway/stairs 0.4–0.8 kW 0.9–1.8 kW rated 600 × 600mm double panel A proper heat loss survey by a MCS-certified installer will give accurate figures for each room. These values are illustrative — do not use for installation specification. ## Do You Need to Replace Your Radiators? The answer depends on three things: your current radiator sizes, your home's insulation level, and the flow temperature your heat pump will run at. Check whether [your home is suitable for a heat pump](/ashp/which-houses-are-not-suitable-for-heat-pumps). Scenario Likely Outcome Modern double-panel radiators + well-insulated home Mostly adequate — minor upgrades in 1–2 rooms Old single-panel radiators throughout Significant upgrades likely in most rooms Mix of old and new radiators Survey needed room by room Open-plan spaces or large living rooms Almost always need larger radiators or UFH Underfloor heating on ground floor Ideal for heat pumps — rarely needs changes Period property with poor insulation Improve insulation first; radiator changes follow On average, Greentech finds that homes switching from a gas boiler need radiator upgrades in 2–4 rooms out of a typical 4-bedroom house. Very few homes need every radiator replaced. ## How Much Does It Cost to Upgrade Radiators? Radiator upgrade costs vary by size, type, and how many rooms are involved. Here are typical installed prices for a straightforward swap. See our full guide to [air source heat pump installation costs](/ashp/how-much-does-a-heat-pump-cost). Radiator Type Supply Cost Installed Cost Standard double-panel (600×600mm) £80–£120 £200–£350 Standard double-panel (600×900mm) £110–£160 £250–£400 Large double-panel (600×1400mm+) £160–£250 £320–£500 Low surface temp (LST) radiator £180–£300 £350–£550 Bathroom towel rail (HP compatible) £120–£200 £250–£400 Underfloor heating (per m², wet system) £45–£75/m² £90–£130/m² Typical whole-house radiator upgrade cost for a 3-bed semi: **£1,500–£3,500** (2–4 rooms upgraded). This cost is usually included in a full heat pump installation quote from Greentech. ## Radiator Types That Work Best with Heat Pumps Radiator Type Heat Pump Compatibility Double panel convector (Type 22) Excellent — highest output per m² of all panel radiators Single panel convector (Type 11) Poor at low temps — usually needs replacement Fan-assisted radiators Excellent — built-in fan boosts output significantly Underfloor heating (wet/screed) Ideal — designed for low-temp operation (30–40°C) Underfloor heating (overlay/foil) Good — lower output but faster response Towel rails Compatible if correctly sized; most need supplementary panel Cast iron radiators Can work but very high water volume — slow to heat up ## Heat Pump Brands We Install Greentech installs leading heat pump brands, all optimised for UK homes and designed to run efficiently at the lower flow temperatures that make radiator upgrades less disruptive. View our full [air source heat pump installation in Manchester](/heat-pumps) page. Brand Why We Recommend It Vaillant aroTHERM plus Industry-leading COP at low temps; pairs with aroCOLLECT for minimal radiator changes Mitsubishi Ecodan Proven UK track record; quiet outdoor unit; wide capacity range Daikin Altherma R-32 refrigerant; excellent efficiency down to -25°C; compact indoor unit Samsung Gen 6 Latest monoblock design; good low-temp performance; strong warranty LG ThermaV Competitive pricing; reliable in mild UK climates; good installer support ## Frequently Asked Questions ### Do I definitely need new radiators for a heat pump? ### Will my existing radiators work at all with a heat pump? ### Can I keep my existing radiators and just accept slightly lower room temperatures? ### Is underfloor heating better than radiators for heat pumps? ### How long does a radiator upgrade take? ### Will the £7,500 Boiler Upgrade Scheme grant cover radiator costs? Looking for [Manchester ASHP installation](/service-area/manchester/air-source-heat-pump-installation)? Check your eligibility for the [£7,500 Boiler Upgrade Scheme grant](/grants). ## Related Guides & Resources [ ### Heat Pump Systems Samsung & Vaillant air source heat pump installation. ](/heat-pumps)[ ### BUS Grant (£7,500) How to claim your Boiler Upgrade Scheme grant. ](/boiler-upgrade-scheme-bus)[ ### How Heat Pumps Work Understand the technology behind air source heat pumps. ](/ashp/how-do-heat-pumps-work)[ ### Heat Pump Costs Full pricing guide for heat pump installation. ](/ashp/how-much-does-a-heat-pump-cost)[ ### Are Heat Pumps Worth It? Honest analysis of heat pump value for UK homeowners. ](/ashp/is-a-heat-pump-worth-it-in-the-uk)[ ### ASHP Installation Manchester MCS-certified heat pump installers serving Greater Manchester. ](/service-area/manchester/air-source-heat-pump-installation)[ ### Solar Panels Combine solar with a heat pump for maximum savings. ](/solar-panels)[ ### Government Grants All available grants for renewable energy upgrades. ](/grants)[ ### Get a Free Quote Book a free, no-obligation home survey. ](/free-quote) ## Get a Heat Pump Survey Including Radiator Assessment Every Greentech heat pump installation begins with a detailed heat loss survey — room by room, radiator by radiator. We'll tell you exactly what needs changing and give you a full quote before you commit. 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