Heat Pump Guide
Are you considering installing an air source or ground source heat pump for your home? At Dartmoor Energy, we specialise in helping homeowners across Devon, Cornwall, and the South West transition to low-carbon heating solutions. Below, we’ve answered some of the most common questions we are asked.
What is a heat pump?
A heat pump is a highly efficient renewable heating system that extracts heat from the air, ground or water to provide heating and hot water for your home. Even in colder weather, a heat pump can capture ambient heat and transfer it into your home, making it a reliable and eco-friendly alternative to traditional fossil fuel systems like gas boilers. Heat pumps work by transferring heat via a refrigerant cycle, similar to how a refrigerator operates, but in reverse.
How do air source heat pumps work?
Air source heat pumps work by drawing in outside air and passing it over a coil filled with refrigerant. The refrigerant absorbs the heat and evaporates into a gas, which is then compressed to increase its temperature. This heat is then transferred into your home’s central heating system to provide warmth and hot water. The process is energy efficient, typically producing 3-4 units of heat for every 1 unit of electricity used.
How do ground source and water source heat pumps work?
Ground and water source heat pumps operate by absorbing heat from the earth or a water source, such as a lake or groundwater, through a series of buried or submerged pipes filled with a heat-transfer fluid. The fluid absorbs heat and is circulated to a heat pump, where the heat is transferred to a refrigerant. The refrigerant evaporates into a gas and is then compressed to raise its temperature. This heat is used to warm your home and provide hot water. These systems are highly energy efficient, typically generating 3-5 units of heat for every 1 unit of electricity consumed.
​
​
​
What types of air source heat pumps are there?
There are two main types of air source heat pumps:
-
Air-to-Water Heat Pumps: These are the most common and transfer heat into your home’s wet central heating system, such as radiators or underfloor heating. They are used to heat both your home and your hot water.
-
Air-to-Air Heat Pumps: These systems provide heating through air distribution, delivering warm air directly into your home, but only a few model can heat hot water too. Air-to-air systems can also offer cooling in the summer.
​
​
Is my home suitable for a heat pump?
In order to check whether your home is "heat pump ready" you will need a comprehensive heat loss survey complete. A heat loss survey will confirm the exact heat requirement for each room and for the property as a whole. The surveyor will then be able to determine what size heat pump and what size radiators the property requires, in order for a heat pump to adequately heat the property all year round. The surveyor will check the existing pipework, existing radiators, electrical connection and heat pump location.
​
Dartmoor Energy offer a "Is my home heat pump ready?" report service, providing an independent assessment before you approach installers.
​​
How much does a heat pump installation cost?
The cost of installing an air source heat pump varies depending on several factors, including the size of your home, the complexity of the installation, and whether any additional upgrades (such as insulation or radiator replacements) are required. On average, an air source heat pump installation can cost between £12,000 and £20,000. A ground source or water source heat pump requires additional external works, so they are often between £10,000 and £30,000 more expensive than an air source heat pump installation.
There are also grants available to help reduce the cost. The Boiler Upgrade Scheme (BUS) provides up to £7,500 towards the installation of a heat pump. Our team at Dartmoor Energy can help you apply for these grants and ensure you take full advantage of any available funding.
​
How much will I save with a heat pump?
The amount you’ll save depends on your current heating system and energy usage. Homes that switch from oil, LPG, or electric heating will see the most significant savings. On average, heat pumps are three to five times more efficient than traditional gas or oil boilers, meaning you’ll reduce your energy bills while lowering your carbon footprint.
​
While savings will vary, the long-term benefits of a heat pump include lower running costs and reduced reliance on fossil fuels. Combined with the Boiler Upgrade Scheme, many homeowners find the initial investment pays off within a few years.
​
Are there any grants available for heat pumps?
Yes! The Boiler Upgrade Scheme (BUS) offers grants of up to £7,500 to help with the upfront costs of installing a heat pump. This government initiative is part of the UK’s plan to reduce carbon emissions and move towards net zero by 2050. To be eligible, you only need to replace an existing fossil fuel or electric heating system, or being building a self-build property.
​
Are heat pumps loud?
No. Modern heat pumps operate between 40db to 60db at their peak, up to 5m in front of the fan. To put this into comparison, this is the same volume as a fridge freezer fan or a light conversation. Heat pumps will only make a noise when the fan is turned on to provide heating. Decibel data can be found on most heat pump manufacturers websites, giving an idea of the peak decibels produced by their heat pumps. Listen to the video to the hear noise level!​​​​
​​​
What type of emitters can you use with a heat pump?
Heat pumps use a wet based heat distribution system. This means, heat pumps can be used with radiators or underfloor heating. Heat pumps can also use a dry heat exchanger and header unit, often referred to as air conditioning units.
​​
​
What temperature do heat pump heat central heating circuits to?
The lower the central heating flow temperature, the higher the efficiency or the heat pump and the lower the running costs. Typically, a radiators system will be designed for a maximum flow temperature of 45C and an underfloor heating system will be designed for a maximum flow temperature of 35C. However, the design flow temperature will depend on a number of factors - heat loss calculations, available space, heating system limitation, personal preferences. Heat pumps work best when set to weather compensation mode, which allows the heat pump to alter the flow temperature dependent on the outside temperature.
Can heat pumps heat hot water for hot taps?
Yes, heat pumps will sufficiently heat the home's hot water cylinder. The hot water cylinder will be linked to the home's hot water taps, providing hot water where needed.
What temperature do heat pumps heat hot water?
Heat pumps can heat hot water cylinders to 70C, when using an R290 heat pump. However, typically, the most efficient and comfortable level to store hot water is between 48C and 55C. A 60C+ legionnaire cycle should be done every 7-14 days when storing water below 60C, to ensure bacteria in the tank is killed.
What temperature can a heat pump heat my home to?
Heat pumps have the ability to heat a property to 35C+ (albeit at great expense!). A heat pump is more than capable of heating a property around 18-22C all year round. The crucial point is to ensure that the heat pump and radiators have be designed to reach your desired temperature, on the average coldest day of the year.
​
What size heat pump do I need for my home?
The size of the heat pump required for each property depends on the property's total heat loss. The heat loss figure for each property is unique. In order to work out the total heat loss of a property, you must look at the building's construction, insulation levels and geographical location. The surface area of each room must be broken down into the following sections - floor, walls, roof, openings. Thermal transmittance calculations must then be made for each section, based on the u-value of each element that makes up that particular surface. Predicted temperatures for the space adjoining each surface area must also be taken into account. Finally, air changes per hour must be considered to understand how quickly the heat will escape through air infiltration.
A heat loss survey is a specialist assessment requiring expertise in building construction, as well as comprehensive software to calculate the final heat loss figure.
​
Do I need to add insulation to my home before I install a heat pump?
No, you don't need to add insulation to have a heat pump. However, adding insulation allows the heat pump and radiators to be reduced in size. These reduction may be essential to make a heat pump viable in the property. Adding insulation will also reduce the running costs of the system. This information is relevant for all heating systems.
​
What size radiators do I need with my heat pump?
Heat pump heating systems run at lower temperatures, which often means that radiators need to be upsized to meet the required heat output. In order to correctly size a radiator, a heat loss survey must be completed to know the heat loss of each room. Once the heat loss of a room is known, this can then be matched to a radiator with the desired heat output.
​
Note: Radiator heat outputs on manufacturer websites are often based on a central heating temperature of 70C (dT50) and slower flow rates than a heat pump. Always contact the supplier, or installer, and ask what heat output the radiators will produce at a flow temperature of 45C (dT25).
What size pipes do I need for a heat pump?
Heat pumps require faster flow rate than a conventional boiler. As a result, the piping in a property needs to be sufficiently sized to accommodate this. When combining a heat pump with radiators, the installer will need to design the system to ensure that the pipework can output enough heat based on the heat loss calculations, flow temperature, flow rate and radiator size. Typically, 3 bedroom 1990s cavity wall built property would require 28mm main feed pipework and 15mm pipework the radiators.
​
What size pipe spaces do I need for my underfloor heating?
Underfloor heating with a heat pump is the most efficient method of heating, due to being able to run the system at a lower temperature. Room-by-room heat loss calculations and floor finish thermal conductivity calculations should be complete to determine the correct pipe spacings. If the pipes are too far apart, the flow temperature will need to be hotter. If the pipes are too close together, the floor may exceed safe levels and the required flow and return temperature difference (dT) may not be met. All rooms should be equally balanced to the same flow temperature, so that they heat at an equal rate.
​
Is my electricity supply adequate for a heat pump?
The total electricity supply required for a heat pump will depend on the make, model and maximum heat output. A 100amp main incomer fuse is often the first check done by our surveyors when assessing a property. This is the largest fuse available on a single-phase connection, and will adequately supply most domestic heat pumps. The average heat pump will have a maximum demand of 8amps - 40amps. However, properties with a high heat loss may require a larger heat pump or multiple. A three-phase connection can be installed where the power supply is insufficient, however, this connection upgrade can come at great expense.
​
Do I need to tell my Distribution Network Operator (DNO) about my heat pump?
Yes. Your installer will likely take care of this, but it must be done. Depending on the type of heat pump being installed, it will either need to be done pre or post install. If the heat pump has been check and certified, it will be on the ENA register - meaning the system can be installed without any pre-approval. If a non approved heat pump or multiple approved heat pumps are being installed, pre-approval will be required. The DNO will check that your fuse is adequate to handle the potential maximum demand of your heat pump. The DNO will also check that the local transformer and infrastructure can handle the additional load being connected to the grid.