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What Size Heat Pump Do I Need?

what size heat pump do i need

Deciding on the right size heat pump for your home can be daunting. Too small, and it won’t efficiently heat or cool your space; too large, and you’ll face unnecessary energy costs. It’s a crucial decision that impacts your comfort and utility bills.

We understand the importance of getting this right, so we’re here to guide you through the process. This article will help you assess your home’s requirements, considering factors like square footage, insulation, and climate. With our expert advice, you’ll find the perfect heat pump size to keep your home comfortable year-round. 

Let’s get started on finding the ideal solution for your needs!

Does heat pump size matter?

Yes, it does. Properties come in all shapes and sizes, each with different heating needs. Just as larger homes need boilers with higher outputs, heat pumps are the same. 

Failing to choose the right size heat pump can lead to the following issues: 


Using a small heat pump in a large house is like expecting one radiator to heat your entire property. Buying a smaller heat pump can save money initially, but it will work overtime to heat your property, resulting in higher energy bills. 

In contrast, large pumps are too powerful for smaller properties. Their increased risks of short cycles could cause damage to the pump, leading to early replacements. 

Maintenance costs 

Heat pumps last between 15 and 20 years on average, but well-maintained models can exceed 25 years. However, if the pump isn’t compatible with your property, it will inevitably lead to higher levels of maintenance and repairs. 

You might also need to replace the pump early, placing you under significant financial strain. 

Humidity and moisture 

With the summers seemingly getting hotter each year, buying a large heat pump might seem like a great way to keep your home cool. Unfortunately, these pumps can create more moisture and humidity in the air, leading to mould growth. 

Mould can lead to numerous health complications, but it’s avoidable when you choose the right generator size. 

Inadequate heating 

Small heat pumps will struggle to heat large homes or older properties with poor insulation. Underestimating your needs could lead to inadequate heating during the colder months. 

Most people try to fix this by adding other heating sources. Sure, your property will be warm, but electric heaters can skyrocket your energy bills. 

Recommended heat pump sizes 

Water-source heat pumps can be beneficial for properties near water, but the complexity of installing them often means people opt for ground or air-source pumps instead. 

Whether you opt for an air or ground-source pump, one rule should be followed: the bigger the property, the larger the pump should be. 

Let’s explore the general recommendations for heat pump sizes. 

Property Type Ground Source Heat Pump Output (kW)Air Source Heat Pump Output (kW)
Flat or house with two bedrooms4kW 5kW 
Three bedroom house that lacks insulation 8kW 9kW 
Four bedroom house that lacks insulation 15kW 16kW 
Well-insulated four bedroom property 8kW 9kW 
Five bedroom property with insulation 15kW 16kW 

Remember, the following outputs are guidelines only. The heat pump size you’ll need depends on numerous factors. 

Things to consider when choosing a heat pump

While the above outputs are guidelines, the heat pump you choose will need to fit your property size and provide year-round functionality. Here’s what you should consider when selecting a pump. 

Property and room size 

All properties are different, and a terraced three-bedroom house might be much smaller than a detached home with three bedrooms. Room size also makes a significant difference, as lounges are heated longer than bedrooms. 

If you have a three-bedroom house but each room is larger than average, it’s best to choose heat pumps with a higher output. 


The UK is known for its volatile climate, but some areas experience more temperature fluctuations than others. Considering that Scandinavian countries use heat pumps, even the coldest UK locations can use them—but size will make a significant difference. 

For example, if you live in Scotland or Northern England, your heat pump will work harder in winter than in homes in South or West England. 


A well-insulated property can make a massive difference to your energy bills. Unfortunately, many older homes struggle to maintain consistent temperatures due to heat loss, making heat pumps work harder. 

Before May 2024, homes could only access funds from the Boiler Upgrade Scheme if they met the minimum insulation criteria, but applications after this date now don’t have minimum insulation guidelines (Ofgem).

However, not insulating your property means your heat pump will work over time, and you’ll need a larger model. 

Underfloor heating 

If you plan on investing in a heat pump, under-floor heating can work with lower outputs to reduce energy bills and ensure optimal performance. 

Working out ground and air-source heat pump size

Figuring out which heat pump you need can be challenging, so many people choose a professional heat pump installation service. 

Certified professionals will assess your property’s size, location and insulation, then use this information to calculate the right heat pump output. 

Heat pumps with outputs of 4 kW to 12 kW are usually fine for most UK homes, but a lack of insulation might mean it’s best to choose a 16 kW pump.

What do professionals recommend?

Generally speaking, 10 metres squared equals 1 kW, so a small flat could use a 4 kW pump, while an average 85-square-metre property would need a 9 kW pump. Remember, if you live in an older property, it might lose heat quickly. 

Using a professional service is the best way to determine your heat pump needs and ensure you get a compatible size. 

The bottom line 

Heat pumps will continue to play significant roles in heating and cooling properties across the UK. Their unique design can reduce our reliance on fossil fuels and pave the way for a more sustainable future. 

If you’d like to invest in a heat pump, we offer bespoke heat pump installations tailored to your specific needs, home type, and budget.

Get in touch with us today and explore your options.

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