A Comparison Between Air Source v Ground Source Heat Pumps

With the ever-rising cost of fossil fuels and a growing emphasis on sustainable living, many UK homeowners are turning to heat pumps as a sustainable and cost-effective heating solution.

But when faced with the choice between an air-source heat pump (ASHP) and a ground-source heat pump (GSHP), how do you decide which one is right for you?

This article aims to offer insight into these two popular options, breaking down their differences, pros and cons, and costs, to help you make an informed decision.

Table of Contents

What Is a Heat Pump?

A heat pump is a device that moves thermal energy from one place to another. A familiar example of this technology is found in our everyday refrigerators.

It can draw latent warmth from the air outside or the ground and bring it inside your home. Once inside, this energy is compressed, and the heat is distributed through a series of coils, warming up your living space.

Though a heat pump does use a bit of electricity, it is considered highly efficient and eco-friendly since it doesn’t burn fuel to generate heat.

Generally, there are two main types of heat pumps based on their heat source: air and ground – both of which are becoming common features in modern, sustainable homes.

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What’s the Difference Between Air Source and Ground Source?

Where these pumps draw their heat from is the key difference between the two. Air-source heat pumps pull heat from the air outside, and ground-source heat pumps absorb heat from underground. This means their installations are quite different.

Differences in efficiency

Air source heat pumps’ efficiency can be tricky to measure as their performance is usually tested based on a 7 °C inlet temperature, which doesn’t always match real weather conditions.

Ground source heat pumps are tested at a more realistic 0 °C inlet temperature, providing a more accurate idea of their efficiency. Plus, with the help of smart controls and time-of-use tariffs, ground-source heat pumps can shift their electricity use to cheaper or greener times of the day.

air source heat pump

Installation Costs of Air Source Heat Pump

The cost to install an air source heat pump, the most common type in the UK, can vary widely depending on several factors. The size of your property is a significant consideration; larger spaces require more powerful heating systems, thus raising the cost.

Insulation is another crucial aspect; poorly insulated properties necessitate the heating system to work harder to maintain a stable temperature, which might impact the cost.

According to the Energy Saving Trust (EST), the typical installation cost for an air source heat pump system ranges from £7,000 to £13,000.

heat pump

Installation Cost of Ground Source Heat Pump

pting for a ground source heat pump comes with a higher upfront cost, with prices usually ranging from £18,000 to £50,000. This cost covers the pump equipment, the installation, and the groundwork. The digging and laying of pipes can be a big part of the cost, especially if you need deep holes rather than just trenches.

If your house and garden are bigger, this might mean more digging and a higher price. However, there are government grants available to help out.

Running Costs of Air Source Heat Pump

Running an ASHP tends to be pricier than using a gas boiler, as electricity, which powers the heat pump, costs significantly more than gas. The EST emphasises this point but also suggests that this cost difference might decrease in the future.

On average, an ASHP has a yearly running cost of about £1,122; however, this can change quite a bit depending on where you live in the UK. A typical British home uses around 3,300 kWh of electricity annually. Given the average electricity rate of 34p per kWh as of 2023, operating an ASHP would cost around £1,122.

heat pump

Running Costs of Ground Source Heat Pump

Ground source heat pumps don’t differ much in terms of their running price but can be a bit more affordable. In the UK, a typical three-bedroom home will pay an average running cost of around £1,048 annually.

These pumps are more consistent in efficiency throughout the year compared to ASHPs because the ground temperature stays fairly stable, while air temperature does not.

For those living in southern parts of the UK, where temperatures are generally warming, running a ground source heat pump could be cheaper than a gas boiler. Plus, homes with better insulation or heat pumps with efficiency ratings above 300% may experience lower running costs.

Which Type of Heat Pump Is More Efficient?

Air source heat pumps are an efficient option for both heating and cooling your home, with the potential to achieve efficiencies exceeding 400%.

This means they can be four times more effective than older heating systems that run on gas, oil, or propane, which usually work at about 80% – 97% efficiency. This is because air-source heat pumps move heat around instead of making it by burning fuel. However, their efficiency goes down during the colder winter months.

Ground source heat pumps don’t have this problem, as they benefit from a consistent and stable heat source, which is not affected by outdoor temperature variations. This makes them more efficient at around 450% throughout the year.

Pros and Cons of an Air Source Heat Pump

Pros

  • High efficiency: ASHPs have a high energy efficiency rating, providing warmth and comfort without using too much power.
  • Minimal power consumption: These systems don’t need a lot of electricity to work, keeping energy bills low.
  • Long lifespan and minimal maintenance: ASHPs tend to last for about 20 years, and they don’t require much maintenance.
  • Affordable: While they do have pricey upfront and installation costs, ASHPs are cheaper than other alternatives, including ASHPs.

Cons

  • Climate adaptability: In colder climates, air source heat pumps might not work as efficiently, making ground source heat pumps a better choice in these cases.
  • Potentially higher electricity bills: Even though air source heat pumps use less energy, you might end up paying more for electricity.

Pros and Cons of a Ground Source Heat Pump

Pros

  • Cost-effective: GSHPs can save homeowners a lot on energy bills.
  • Highly efficient: These pumps are known for their impressive efficiency ratings, surpassing traditional gas heating systems.
  • Quality low-carbon alternative: They use the Earth’s natural heat and electricity to warm your home.
  • Low maintenance: A ground source heat pump doesn’t need much maintenance. It’s a reliable system that doesn’t require yearly check-ups like a boiler.

Cons

  • Expensive upfront costs: The upfront and installation costs are steep. Even with financial assistance from schemes, the upfront cost is a major commitment.
  • Requires a large outdoor space: Your garden will need to be big enough to accommodate the installation of underground pipework.
heat pump alternative to boiler

FAQs

Choosing which type – air source vs ground source heat pump – is best suited for your home depends on various factors, including cost, space availability, and efficiency needs.

ASHPs are generally more affordable and adaptable, fitting well in smaller spaces and older buildings. They’re easier to install but tend to be less efficient during colder months as they rely on outside air temperatures. In moderate climates, they perform exceptionally well, providing a cost-effective heating and cooling solution.

Ground source heat pumps, on the other hand, require a much higher upfront investment and more space for installation. Although, they offer consistent efficiency throughout the year. Despite the complex installation process, GSHPs are quieter, have longer life spans, and prove to be more cost-effective in the long run.

If you’re considering installing a heat pump unit, it’s wise to explore the various grants available to help offset the installation costs.

The ECO4 scheme is a good option to consider, which helps qualifying homes get a heat pump and better insulation. If you or someone in your home receives certain benefits, you might even be able to get the heat pump for free.

Both air and ground source heat pumps can be used to replace a boiler. A heat pump can be used to perform the same functions as a boiler, including heating hot water to warm your underfloor heating and radiators. This makes installing a heat pump a good, eco-friendly alternative when it comes time to replace your boiler.

Conclusion

Choosing between an air-source heat pump and a ground-source heat pump hinges on factors like your budget, space, and efficiency needs. ASHPs are more budget-friendly and versatile, yet less efficient in colder weather. GSHPs demand a higher upfront investment and space but offer consistent efficiency and longevity.

Ultimately, both options offer reliable heating and cooling solutions, but considering your personal situation will help determine which system is more suited for your home.