How to choose the right type of heat pump for your home

What is a heat pump and how does it work?

A heat pump is a device that moves heat from one place to another using electricity, working on a principle like a refrigerator in reverse. Instead of burning fuel to generate warmth, it extracts heat from an external source, whether air, ground, or water, and transfers it indoors. This process, based on evaporation, compression, condensation, and expansion, allows a well-designed heat pump to deliver up to four units of heat for every unit of electricity consumed.

In the UK, the adoption of residential heat pumps has expanded rapidly in recent years. By the end of 2023 there were over 21 million heat pumps installed across the EU.

Understanding the basics of how heat pumps work makes it easier to evaluate the different system types without getting lost in technical jargon. For a more detailed explanation of the process, read our guide to how heat pumps work.

The main types of heat pumps and how they work

The efficiency and suitability of a heat pump are fundamentally determined by its heat source. Air, ground, and water each offer different levels of temperature stability and seasonal performance, and this difference is what shapes the three main categories of heat pump systems available today.

Air source heat pumps

Air source heat pumps extract heat from outside air and remain effective even in winter, with modern models operating efficiently down to −28°C. They are the most common type installed in European homes today, and for good reason: they are versatile, relatively straightforward to install, and suited to a wide range of property types.

ASHPs provide both space heating and domestic hot water, making them a practical all-in-one solution for most households. They can reduce running costs by up to 50% compared to traditional direct electric heating systems, because they move heat rather than generate it. Actual savings depend on your home’s insulation, heat distribution, and electricity tariff. Seasonal performance varies, and efficiency does decline at very low outdoor temperatures, which is worth factoring into your assessment if you live in a colder area.

Variations within air source systems

Air source heat pumps come in several configurations, each suited to different heating needs:

• Air-to-air systems: Blow heated air directly into rooms via indoor units. Ideal for smaller spaces or where a wet heating system is not in place. They do not produce domestic hot water.
• Air-to-water low-temperature systems: Circulate hot water through radiators or underfloor heating. They operate more efficiently than higher-temperature systems and typically achieve Seasonal Coefficient of Performance (SCOP) values of 3.0 to 3.5. They work best with larger heat emitters.
• Air-to-water medium-temperature systems: Offer a practical middle ground, suitable for homes with standard radiators that have been appropriately sized.
• Air-to-water high-temperature systems: Deliver water at up to 75°C, making them compatible with existing conventional radiator systems and a strong option for retrofits. They offer slightly lower efficiency than LT systems but reduce the need for significant emitter upgrades.

Air source heat pumps also come in two installation formats: a monobloc unit, where all components, including the refrigerant circuit, sit in the outdoor unit and only water pipes run into the home, and a split system, where refrigerant pipework connects the outdoor unit to an indoor unit inside the property. Monobloc units are simpler to install and service; split systems can offer more flexible indoor placement.

Regular maintenance, including filter cleaning and periodic refrigerant checks, is essential across all variants to maintain long-term performance and reliability.

Ground source heat pumps

Ground source heat pumps, sometimes referred to as geothermal heat pumps, extract heat from underground, where temperatures in Europe remain relatively stable at around 8-12°C throughout the year. This stability enables high and consistent efficiency, with SCOP values frequently exceeding 4.0, and translates into lower long-term running costs compared with air source systems.

There are two main installation approaches. Horizontal ground loops are buried across a large garden area around one metre deep, making them cost-effective where sufficient land is available. Vertical boreholes drill down to greater depths, requiring less surface space but involving more complex and expensive groundwork. Both approaches deliver heat reliably, even in the middle of winter. Both configurations use a closed loop system, in which a sealed circuit of fluid circulates through the ground and back to the heat pump. In some cases where groundwater is accessible, an open loop system can be used instead, drawing water directly from an aquifer and returning it once heat has been extracted, though this requires additional environmental permitting.

Ground source heat pumps pair particularly well with underfloor heating due to the low-temperature delivery that both systems favour. They are well suited to new builds or properties with substantial outdoor space. Indoor components typically last around 20-25 years with correct, regular maintenance, contributing to the overall long-term value of the system.

Water source heat pumps

Water source heat pumps extract heat from lakes, rivers, or underground aquifers, where water temperatures remain relatively stable across the seasons. Their efficiency potential is similar to ground source systems.

In practice, these systems are less common in residential settings because they require access to a suitable water body and are subject to environmental regulation, including water abstraction permits and ecological impact assessments. Where conditions allow, they offer high-performance heating and hot water. For most homeowners, the regulatory and logistical requirements mean that air or ground source solutions are the more practical starting point.

Hybrid heat pump systems

Hybrid systems combine a heat pump with an existing gas or oil boiler, automatically switching between the two depending on outdoor temperatures or energy prices. During most of the heating season, the heat pump handles the load; the boiler activates only when temperatures drop very low or demand spikes.

This configuration is particularly useful for older properties where full electrification is not currently practical, or where insulation improvements are planned in stages. It allows homeowners to reduce fossil fuel consumption gradually without requiring full-scale renovation upfront. That said, most installers today are moving towards fully electric heat pump solutions, and hybrids are best viewed as a transitional option rather than a long-term endpoint.

Comparing efficiency across heat pump types

Efficiency in heat pump systems is measured using the Seasonal Coefficient of Performance (SCOP) .

• Air source heat pumps typically achieve SCOP values of 3 to 4 under standard European seasonal conditions. Performance drops during very cold spells but recovers as temperatures rise.
• Ground source and water source systems can consistently exceed SCOP values of 4, reflecting the advantage of a stable heat source that does not fluctuate with weather.

Real-world efficiency is also shaped by system design, installation quality, and the heat distribution in your home. A well-designed air source heat pumps paired with underfloor heating can sustain SCOP values of 3.2-3.5 even through winter. Understanding these figures helps set realistic expectations and compare systems on equal terms.

How radiators and underfloor heating affect heat pump performance

The heating distribution system in your home is as important as the heat pump itself. Underfloor heating operates at low flow temperatures, typically 35-45°C, which is exactly the range where heat pumps deliver their best efficiency. Pairing an ASHP with underfloor heating is one of the most efficient combinations available for residential use.

Radiators can also work well with heat pumps, but they generally need to be larger than those specified for a gas boiler to function effectively at lower flow temperatures. In retrofits, this often means replacing or supplementing existing radiators. High-temperature heat pumps reduce the extent of this upgrade by delivering water at higher temperatures, though at a modest efficiency cost. The choice of emitter has a direct and measurable impact on annual running costs.

Understanding heat loss in your home

Heat loss is the rate at which a building loses warmth to the outside, and it is the single most important variable in determining what size of heat pump you need. It is influenced by insulation quality, window glazing, roof and wall construction, and the overall airtightness of the building. A detailed breakdown of how these factors affect suitability is available in Daikin’s guide to heat pump suitability.

A poorly insulated home forces the heat pump to work harder, which reduces efficiency and increases running costs. Improving insulation and glazing can reduce heat loss by up to 40%, often enabling a smaller, more cost-effective system. Accurate heat loss calculation, carried out by a qualified professional, forms the foundation of a well-designed installation. Choosing a heat pump without this step is one of the most common and costly mistakes homeowners make.

Not every home is equally well suited to a heat pump. Properties with very high heat loss, typically older buildings with solid walls, single glazing, and no loft insulation, may require significant upgrades before a heat pump can perform efficiently. Homes without adequate outdoor space for an air source unit, or without access to land or a water body for ground or water source systems, face additional constraints. A professional assessment will identify what, if anything, needs to change before installation.

How to choose the right heat pump

Choosing the right heat pump means treating your home as a complete energy system, not selecting a unit in isolation. A structured approach to this decision avoids the most common pitfalls and ensures the system performs well over its full lifetime. To guide your thinking, consider these three questions before speaking to an installer:

• What heat source is available to me? Air source suits most homes. Ground source requires outdoor space. Water source requires proximity to a suitable water body. Your answer immediately narrows the options.
• What does my heat distribution look like? Underfloor heating is naturally compatible with low-temperature heat pumps. Radiators may need to be upgraded or replaced, depending on the heat pump type you choose.
• How well insulated is my home? A professional heat loss calculation tells you the capacity the system must meet. This figure drives every sizing decision and affects long-term running costs.

For most homes, an air source heat pump is the most practical starting point. Where outdoor space and budget allow, a ground source system will deliver higher seasonal efficiency. The best type is always the one correctly matched to your specific property.

Beyond these three questions, consider your budget across the full lifetime of the system, not just the upfront price. A system that is poorly matched to your property may cost less to buy but significantly more to run.

Installation: technical factors and the role of your installer

Technical installation factors

Proper heat pump installation has a direct and lasting effect on system performance. Outdoor unit placement affects airflow, efficiency, and noise levels, so positioning should be carefully planned to avoid obstructions while respecting neighbours. Indoor units must integrate cleanly with existing plumbing and the heating distribution system. Pipework routing, electrical connections, and condensate drainage all require careful design to maintain efficiency. Commissioning, the final process of verifying refrigerant levels, controls, and performance, is not a formality: it is what ensures the system delivers what it was designed to.

Choosing the right installer

An experienced, Sustainable Home Specialist is as important as the heat pump itself. A qualified professional assesses your property, conducts the heat loss calculation, recommends the appropriate system type and capacity, and takes responsibility for the quality of the installation. Installers must be trained in refrigerant handling, electrical safety, and hydraulic balancing. A well-installed system minimises breakdowns, reduces maintenance costs, and protects your investment over the long term. Reputable installers also provide ongoing support and can advise on system upgrades as technology evolves.

Running costs and long-term value

Heat pumps typically use less electricity than direct electric heaters because they move heat rather than generate it, meaning the same level of warmth is delivered with less energy. Air source heat pumps operate at a Coefficient of Performance (COP) of around 3.5 to 4, meaning they produce three and a half to four times more heat energy than the electrical energy they consume. Actual running costs depend on several factors: the efficiency of the system, the level of heat loss from the home, the flow temperatures required by the distribution system, and the electricity tariff. An air source heat pump costs approximately £800 - £1000 per year to run for heating, broadly comparable with a modern gas boiler at current energy prices. Homes with good insulation and low-temperature distribution are in the best position to benefit from lower bills. Broader energy-saving strategies to complement your heat pump installation are also worth exploring.

Upfront heat pump costs vary depending on system type and installation complexity, and can appear high compared with a boiler replacement. Viewed over the lifetime of the system, however, lower energy consumption can offset a significant portion of that initial investment. Indoor components are built for long operational lifespans, and ground-based infrastructure is designed for extended use. When government incentives, energy savings, and predictable maintenance requirements are all considered together, heat pumps represent a long-term investment in both household comfort and lower-carbon heating.

Retrofitting and future-proofing your home

Older buildings present specific challenges: higher heat loss, existing radiator systems, and less airtight construction all affect how a heat pump performs. Retrofitting requires a realistic assessment of what improvements are needed alongside the installation, whether that means adding loft insulation, upgrading glazing, or replacing radiators. Hybrid systems can provide a useful interim solution for properties where full electrification is not immediately practical.

Modern heat pumps are also well suited to new builds and recently renovated homes, where they often pair with underfloor heating, smart controls, and on-site solar generation. This combination supports steady, even indoor temperatures while reducing reliance on grid electricity. Refrigerant technology is also evolving, with newer low-GWP (global warming potential) refrigerants progressively replacing older options across the industry, reducing the direct environmental impact of the systems themselves. As European buildings move towards lower-carbon heating, heat pumps are increasingly considered a future-ready choice: they align with ongoing electrification trends and are compatible with evolving efficiency standards.

Common mistakes to avoid

Understanding the limitations and common pitfalls of heat pumps helps you avoid costly mistakes. The main disadvantages tend to appear when systems are poorly matched or installed, and they include:

• Oversizing or under sizing the system: An oversized heat pump short cycles inefficiently; an undersized one struggles in cold weather. Only an accurate heat loss calculation prevents this.
• Ignoring heat distribution compatibility: Pairing a low-temperature heat pump with undersized radiators reduces efficiency and comfort. The full heating system must be designed together.
• Focusing only on upfront cost: A lower purchase price can translate into higher running costs if the system is poorly matched. Total cost of ownership matters more than the headline price.
• Underestimating installation complexity: Choosing an uncertified or inexperienced installer risks poor commissioning, early breakdowns, and costly rectification work.

Skipping the heat loss assessment: This is the foundation of the entire selection process. Without it, no sizing decision is reliable.

Conclusion and takeaways

The right heat pump is not simply the most efficient model on the market: it is the system that best matches your property’s heat loss, available heat source, and heating distribution. Air source systems suit most homes; ground and water source options deliver higher efficiency where conditions allow. Correct sizing, professional installation, and a realistic assessment of your property are what determine long-term performance, not brand or headline figures alone. Contact a certified installer to get your home assessed and explore which heat pump system is the right fit for you.

• Heat pumps are a family of technologies, not a single product: air source, ground source, and water source systems each suit different property types and conditions.
• Air source heat pumps are the most common residential choice, offering flexibility, simpler installation, and suitability for most urban and suburban homes.
• Efficiency depends on heat source, system design, and distribution: ground and water source systems achieve higher SCOP values, but air source systems perform well when correctly sized and installed.
• Heat loss calculation is the essential first step: it determines the correct system size and prevents the costliest selection errors.
• Professional installation is as important as the heat pump itself: correct commissioning, hydraulic balancing, and ongoing support are what ensure the system delivers on its design performance.

Contact a Sustainable Home Specialist to get your home assessed and explore which heat pump system is the right fit for you.