--- title: "Swimming Pool Heat Pump Sizing Guide | Appian" description: "How to size a swimming pool heat pump correctly the first time — avoid undersized units that never heat and oversized units that waste money." lang: en-GB json-ld: | [ { "@context": "https://schema.org", "@type": "Article", "headline": "Swimming Pool Heat Pump Sizing Guide", "description": "An undersized pool heat pump will never reach temperature. An oversized one wastes money upfront and runs inefficiently. Here's how to calculate the correct size for your pool.", "datePublished": "2026-02-18", "author": { "@type": "Person", "name": "Craig Ball" }, "publisher": { "@type": "Organization", "name": "Appian Heat Pumps", "url": "https://www.appianheatpumps.com" }, "mainEntityOfPage": { "@type": "WebPage", "@id": "https://www.appianheatpumps.com/blog/swimming-pool-heat-pump-sizing-guide" } }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://www.appianheatpumps.com/" }, { "@type": "ListItem", "position": 2, "name": "Blog", "item": "https://www.appianheatpumps.com/blog" }, { "@type": "ListItem", "position": 3, "name": "Swimming Pool Heat Pump Sizing Guide" } ] } ] --- [ Special Offer Air Conditioning Fully Installed from £1,100 → ](/contact) 12 Appian Way, Chineham, Basingstoke, RG24 8BH Fastest reply → [07481 552059](tel:07481552059)| [01256 672332](tel:01256672332) [![Appian Heat Pumps](/assets/logo-DXHDe5EY.png)](/) Services Service Areas [About](/about)[Our Work](/our-work)[Blog](/blog)[Reviews](/reviews)[Contact](/contact) Call now — fastest reply [07481 552059](tel:07481552059)[Landline: 01256 672332](tel:01256672332) [Request Estimate](/contact) [Call 07481 552059 Fastest reply ](tel:07481552059)[Get Estimate](/contact) 1. [Home](/) [Blog](/blog) Swimming Pool Heat Pump Sizing Guide Installation Guide # Swimming Pool Heat Pump Sizing Guide An undersized pool heat pump will never reach temperature. An oversized one wastes money upfront and runs inefficiently. Here's how to calculate the correct size for your pool. By Craig Ball 18 February 2026 6 min read ![Swimming Pool Heat Pump Sizing Guide — featured image](/assets/blog-pool-sizing-DMi-KreM.jpg) ## The Basic Calculation Pool heat pump sizing depends on: pool volume (length × width × average depth), desired temperature rise, whether the pool is indoor or outdoor, whether a cover is used, and local climate conditions. As a starting point: an outdoor pool in southern England with a cover, targeting 28°C, needs approximately 1.2–1.5 kW of heat pump output per cubic metre of water. A 50m³ pool (approximately 10m × 5m × 1m) needs a 60–75 kW unit — we [supply pool heat pumps](/services/swimming-pool-heat-pump-supplier) sized to your exact pool. ## Covered vs Uncovered Pools A pool cover reduces heat loss by 50–70%. This is the single most impactful factor in sizing and running costs. An uncovered outdoor pool may need a heat pump twice the size of a covered one — and will cost twice as much to run. If budget is a concern, investing in a quality thermal cover and fitting a correctly-sized heat pump will always beat installing an oversized unit for an uncovered pool. ## Common Sizing Mistakes The most frequent mistake we see is undersizing. Installers often quote the minimum heat pump size that can theoretically maintain temperature in ideal conditions. In practice, you need headroom for cold spells, heat-up from cold, and periods when the cover is off. Oversizing is less common but still problematic. An oversized heat pump will short-cycle — starting and stopping frequently — which reduces efficiency and increases wear on the compressor, which usually ends in a [pool heat pump repair](/services/swimming-pool-heat-pump-repair). The ideal system runs for extended periods at partial load, and regular [pool heat pump servicing](/services/swimming-pool-heat-pump-service) keeps it there. Craig Ball Founder & Lead Engineer · F-Gas Certified · 15+ Years Craig has installed, serviced, and repaired heat pumps across Hampshire and the south for over 15 years. 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