Answer: A ground source heat pump is typically more efficient than an air source heat pump, and it has better RHI payback. However, a ground source heat pump is more expensive to buy and install at the outset. Horizontal ground source heat pumps are cheaper than vertical ground source heat pumps.
For more information about whether to choose an air source or ground source heat pump system, keep reading.
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We won’t go into detail in this article about the technical differences between an air source heat pump and a ground source heat pump, but it is important to address the key aspects before we continue with our recommendations.
Put simply, an air source heat pump extracts heat from the outside air, and uses it to power heating and hot water. A ground source heat pump, often mistakenly referred to as “geothermal heating”, draws heat energy from the soil beneath the surface of the earth to power heating and hot water. Both of these systems are considered as renewable heating solutions.
Hybrid heat pumps are a third option, using a combination of renewables and fossil fuels. We’ve outlined what hybrid systems offer in this blog post. Typically however, we would always recommend either a ground source heat pump or an air source heat pump. But which is best?
A caveat: We mustn’t generalise too much, because each project has its own suitabilities. These recommendations are based on what we see as typical trends, and should not be taken as gospel because your situation is unique. If you would like to speak to one of our advisors about whether an air source or ground source heat pump is best for you, contact us today.
With regards to the economics, at the outset we usually prefer a horizontal ground source heat pump system as the most desirable renewable heating solution. This technology is the most cost-effective in the medium-to-long-term, although of course it is not always suitable for every property and other options do come into play if this solution doesn’t fit the project.
We recommend horizontal ground source heat pumps for two reasons. Firstly, in the context of ground source vs. air source, the Renewable Heat Incentive (RHI) tariff for ground source is more than double what you can expect for air source heat pumps. This is particularly relevant for larger properties, because there are caps on how much energy you can claim payment for: 20,000kW for air source and 30,000kW for ground source, so if you have a larger house requiring more than 20,000kWh per year it makes sense to look at ground source.
The second reason for our preference is in the context of vertical vs. horizontal ground source heat pumps. We recommend horizontal because the installation is cheaper and less complex due to the equipment and expertise needed for digging trenches vs. boreholes.
A good starting point is to establish whether there is sufficient land for the installation of a horizontal GSHP. If this option is not available due to lack of space available, the second choice would usually be an air source heat pump. A vertical GSHP needs much less space because the boreholes are drilled straight down into the bedrock, and it can have a longer lifespan, though it is more expensive to install.
That said, we do install lots of vertical systems for clients who want to maximise efficiency with a ground source heat pump, and the Assignment of Rights (AoR) offers favourable finance to cover the initial capital outlay of any heat pump installation. This is available all over the UK, and in Scotland homeowners have the added benefit of the Home Energy Scotland Loan.
Most often, a horizontal ground source heat pump presents the best balance of efficiency, cost, and return on investment within the shortest time frame. We will never shoehorn a horizontal ground loop array where it doesn’t belong, but it is usually a good starting point when evaluating your options for switching to renewable heat.
A ground source heat pump is nearly always the most efficient option. A horizontal ground source heat pump is typically the most feasible, although this depends on the space available. An air source heat pump will still offer good RHI tariffs and is considered the easiest and most affordable heat pump to install, especially where space is at a premium. This makes air source heat pumps a very popular choice in the UK.
If installed and maintained correctly, every type of heat pump will provide efficient year-round heat. If you contact Smart Renewable Heat today, our experts will recommend the best heat pump solution for your specific property.
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