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Heat Pump Guide

This guide highlights the areas that should be assessed before retrofitting a heat pump into a property. This guide can be used to make an initial assessment on your home property, or to check the work of an installer. However, we would always recommend obtaining expert guidance from a professional.


Dartmoor Energy offer a specialist report service, looking at the following areas in detail. Dartmoor Energy are partnered with leading installers in the Southwest. After you have received the report, we will obtain quotes from our trusted installer network based on our calculations. To get a quote, click the button at the top of the page. 

What is a heat pump? 

heat pump is a low carbon heating system, used to heat or cool an enclosed space or volume of water. Heat pumps use a refrigeration cycle to absorb thermal energy from a source (air, water or earth). The heat pump increases the temperature of the thermal energy absorbed, via a compressor, and transfers thermal energy to an emitter. 

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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 a heat pump use? 

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 flow temperature do heat pumps heat the central heating circuits to? 

Heat pumps aim for between a 30c and 45c flow temperature, depending on the type of emitter used. Radiators are heated to 45c and underfloor heating is heated to 35c. These lower temperatures allow the heat pump to run at the optimum efficiency, whilst keep the home adequately heated. 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 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 heat the water cylinder to between 50c and 55c. A 60c - 70c legionnaire cycle is done every 7-14 days, using the immersion heater, to eliminate the risk of legionella bacteria growing in the cylinder.  

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, windows. 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 you need to add lots of insulation before installing 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. 

What size radiators do I need with a 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 main feed pipework will need to be sized based on the heat loss of the property. 15mm pipes can then be fed from the main feed to each radiator. 

What size loop spaces do I need for underfloor heating with a heat pump? 

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 require 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 10amps - 50amps. However, properties with a high heat loss may require a larger heat pump. Three-phase heat pumps are available to accommodate this. However, obtaining a three-phase connection can be costly. 

Do I need to tell my Distribution Network Operation (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. 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 can handle the additional load being connected to the grid. 

How does the heat pump connect to my electricity supply? 

The heat pump will have a dedicated breaker slot in your consumer unit (fuse box). A cable will run from the fuse box to an exterior wall, near the heat pump, where an isolator switch will be located. A cable will then run from the isolator switch to the heat pump. 

Our team have been working in the renewable energy industry for over 20 years, collectively. Our extensive knowledge and advanced software provide us with the tools to assess properties and determine whether it is possible to install a heat pump heating system. 

Our office is located in Callington, on the Devon and Cornwall border. Our domestic energy assessors cover homes in and around Plymouth, Torquay, Paignton, Callington, Bodmin, Torpoint, St Austell, Saltash and Tavistock.

To see our competitive prices, click the "Get a Quote" button. 


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