Installing A Heat Pump in an Existing Home  

With the launch of the governments new Boiler Upgrade Scheme, as well as the current uncertainty around energy prices, more and more homeowners are considering replacing their existing heating system with a modern renewable heat pump. In this article we will look in detail at the considerations involved with retrofitting heat pumps into existing homes. 

Here is an overview of the key considerations of installing heat pumps in existing buildings that we will cover in this article:

• Why heat pumps? 
• Is my property suitable for a heat pump? 
• Where do I start? 
• Do I need planning permission to install a heat pump? 
• Informing your District Network Operator (DNO) 
• What else do I need to consider? 
• Your existing heating system 
• Do I have space for a heat pump? 
• Upgrades to your heating distribution  
• Upgrades to your electrics 

Why heat pumps? 

Heat pumps are an incredibly efficient and renewable choice for a property’s space heating and hot water. The systems run on electricity and extract ambient heat from the environment, even at very low temperatures, and for one unit of electricity consumed by the heat pump, the home can receive an average of three or more units of heating. 

Whilst heat pumps are often seen as more suitable for newer properties with high levels of insulation, they are also able to be used in older properties, replacing existing systems such as oil or gas boilers. 

Heat pumps are typically designed to run for longer and at lower temperatures than traditional heating boilers. The lower the flow temperature your heating system can run at whilst heating your property, the more efficient the heating system is to run, resulting in lower running costs.  

Find out more about how heat pumps work.

There are also financial incentives available when installing heat pumps such as the Boiler Upgrade Scheme (BUS). As part of the government’s Heat and Buildings strategy, the Boiler Upgrade Scheme provides upfront grants of £5,000 for air source, and £6,000 for ground source heat pumps when replacing an existing fossil fuel boiler or direct electric heating system. 

Find out more about the boiler upgrade scheme for heat pumps. 

Is my property suitable for a heat pump? 

Although heat pumps are best suited for properties with high insulation levels such as newbuilds or full renovation projects, as long as the system is designed correctly a heat pump system is a good option for most domestic properties. Based in the South West, we have installed many heat pumps into some of the region’s older properties, such as this characterful old cottage in Cornwall, and this grade 2 listed thatched farmhouse in Devon.  

To find out more about these heat pump projects in our case studies click here> 

In older properties with low levels of insulation, it is critical to understand how much heat the property will need to ensure a heat pump with sufficient heating output is specified. This goes back to our design led approach, ensuring that we design & specify the correctly sized heat pump and heating distribution system such as underfloor and/or radiators. Abode Heat’s experience enables us to provide clear advice on the suitability of a heat pump system for your property. 

If you are thinking of applying for the Boiler Upgrade Scheme you will need an EPC (Energy Performance Certificate) for the property that is less than 10 years old. If your EPC is showing recommendations for adding cavity wall or loft insulation, these works will need to be completed before the grant can be awarded – see the scheme details here>

Where do I start? 

The first thing we recommend is a formal MCS (Microgeneration Certification Scheme) room by room heat loss calculation for your property. With existing properties, one of our surveyors will measure up the walls, ceiling heights, windows, and doors, as well as recording information about the property’s construction and insulation levels. The surveyor enters the information into our smart phone app which sends it to our design software where the calculations are completed by our design team 

The final report  lets you fully understand the heating requirements of the property, confirming the current heating and hot water energy consumption. With those figures, we can size a heat pump system that is going to be able to produce 100% of that heat, even in peak heating season, giving you the confidence that the heat pump will keep you warm throughout the year.  

These calculations will also show you estimated running costs of a heat pump system compared to your current boiler, as well as highlighting any radiators that need changing to work efficiently with the heat pump, giving you all the information to make an informed decision on which heat pump is right for you and your property.  

Find out more about our design-led approach to installing heat pumps.

Do I need planning permission to install a heat pump? 

Most heat pump installations are considered ‘permitted developments’ meaning that you don’t need planning permission. There are exceptions to this, so it’s best to double check with your local planning authority, especially if you live in a conservation area or listed building. 

Informing your District Network Operator (DNO) 

As part of a heat pump installation the DNO needs to be informed. Heat pumps with smaller electrical consumptions are classed as “connect and notify” where you only need to inform the DNO after the heat pump installation has taken place. Heat Pumps with larger electrical consumptions are classed as “apply to connect” where you must inform the DNO before the installation happens so they can confirm they are happy with the electrical loading.  

Here in the South West our DNO is Western Power. For our heat pump installations, we will complete the application form with all the heat pump information and send it to Western Power for their approval. 

What else do I need to consider? 

Heat pump installations into newbuild properties are simpler as it is the first heating system put into the property. When looking at using heat pumps into existing homes that already have heating systems in, there other things that need to be looked at as part of the heat pump installation. 

Your existing heating system 

Heat pump systems should be designed to supply 100% of your property’s heating and hot water. There are also great options for hybrid systems for homes with high heating demands (note: these don’t currently benefit from the Boiler Upgrade Scheme) Your existing boiler will need to be decommissioned and removed as part of the installation process which we can help you with. It is important to remember that fuel tanks like oil tanks require specialist removal.  

If your existing system already has a hot water cylinder it will most likely need to be replaced. This is because the heating coil within the tank needs to be sized correctly for a heat pump system. If you have a newer cylinder, there is a chance it might be compatible. If you can take a picture of the data tag on your existing cylinder and send it to us, we can check this for you.

Do I have space for a heat pump? 

Air Source Heat Pumps typically replace existing fossil fuel boilers. This is because air source heat pumps are much less of a “building project” than ground source heat pumps, which either need hundreds of metres of pipes laid in the ground or boreholes to be drilled. Ground source heat pump installations are more expensive than air source heat pumps when you consider the ground works and ground collector materials.  

Air source heat pumps, need a location outside your home where the unit can be fitted to allow a good airflow. The size of the external unit will depend on the heating requirement of the property and can range from smaller single fan units to larger twin fan units. Properties with large heat loads may need a cascade air source heat pump, where two external units work together to meet the property’s heat load. Our design led approach ensures your air source heat pump will  be appropriately located to meet all regulations and installation requirements.

Upgrades to your heating distribution  

The heating distribution is the way that heat is distributed throughout your property – most commonly, radiators or underfloor heating.  

A traditional boiler and radiator system will have a flow temperature of around 70C, while a heat pump runs at a much lower temperature. The exact flow temperature the heat pump can run at depends on the heating distribution and how it has been sized. The lower the flow temperature, the more efficient the system is, but it also means we need to use larger radiators to allow the system to cope with those temperatures.  

In most properties where we install a heat pump system to replace an existing boiler, we size the system to run at a 55 degree flow temperature. This is a balance of the efficiency of the system and practicalities around the size of the radiators.  

When looking at installing a heat pump on an existing heating system, as part of the process some or all of the radiators may need to be replaced with larger ones. Also, with a heat pump system, your radiators will only feel lukewarm to the touch. This is entirely normal and is due to the lower flow temperature of the heat pump compared to your old traditional system.

Microbore pipework  

Usually, we can install new radiators onto the existing pipework in the property, avoiding the disruption of changing large runs of pipework. Standard radiator pipework is 15mm, anything smaller is called microbore pipework and can hinder flow rates we can achieve and affects efficiencies of heat pump systems. Sometimes it is the case that the microbore pipework would need to be replaced and re-piped with standard 15mm pipework for the system to be suitable for a heat pump.

Upgrades to your electrics 

As well as the mechanical installation of the heat pump system, you may need to upgrade electrical supplies for your new heat pump system . This may include power supplies being run from your consumer unit to the external heat pump and internal equipment locations. Depending on the age of your consumer unit, that might need upgrading as well. This will be assessed by our team and incorporated into your system design.

Need Advice? 

If you are thinking about switching your existing heating system and would like some more information, fill out the form below to get in touch and our team will be able to answer any questions and recommend the right system for you and your property.

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Head Quarters:

Exeter Business Park
1 Emperor Way
Exeter
EX1 3QS

Email: customer@abodeheat.com
Facebook: @AbodeHeat
Phone: +44 (0) 333 577 9292