What you need to know about installing an air source heat pump

With the RHI incentivising homeowners and an ongoing focus on more efficient ways to heat properties, now is a good time to embrace low carbon heating technology. An air source heat pump (ASHP) is a popular renewable solution that is suitable for a wide range of projects from small to large.

ASHPs are simple to install, without the need for extensive groundworks, and any plumbing & heating engineer is able to install these units with the help of our MCS support packages, where we take on all of the MCS compliance paperwork and can also commission the system if required.

In this post, we’re taking a closer look at the key stages of installing an ASHP and the support Nu-Heat offers.

Air source heat pump

First off, is the property suitable?


The most important consideration when checking the suitability of an ASHP for a project is how much insulation is present. A well-insulated property will prevent heat escaping, enabling the heat pump to work efficiently at lower flow temperatures, providing the homeowner with an effective, economic heating system.

The insulation present in all new build properties built to Part L1A, and generally those built in the last 10 years, are likely to be suitable for an ASHP.

Older properties will require insulation upgrades such as loft, cavity wall and glazing improvements in line with Part L1B of the Building Regulations.

Access to mains gas

In an existing property, an ASHP is generally suitable only if there is not access to mains gas. This is because the homeowner will see a greater return on investment when compared to the cost of running their previous oil, LPG or electric heating system.

New build properties that have access to mains gas are still suitable for an ASHP, which will perform very efficiently, and this option is often chosen when aiming to create an eco-home that is not reliant on fossil fuels.

Planning permission

Most ASHP installations will fall into the category of permitted development in line with MCS020, so will not require planning permission. Obviously, it is important to check this before getting started!

If the property is listed, in an AONB or Conservation Area or requires more than one heat pump unit, planning permission will be required and the homeowner will have to apply for this.

For more information on ASHPs and planning permission, you can read one of our previous blog posts.

The heat emitter

ASHPs operate most efficiently when connected to low temperature heat emitters, such as underfloor heating or a combination of underfloor and radiators.

If traditional radiators are the preferred option, it’s worth bearing in mind that they will need to be sized in line with the lower water flow temperatures associated with heat pumps; this means they are generally twice the size than those used with a gas or oil boiler.

Installing an ASHP – the key stages

Step 1 – Finding the right supplier and ASHP design

Choosing an experienced supplier is essential when it comes to heat pump system design. You need to be confident that the solution will be efficient and work as expected. Nu-Heat offers the following as standard:

  • Advice and guidance on the suitability of an ASHP for the project
  • Full heat loss calculations for the property in order to correctly size the ASHP
  • An accurate quotation for the system components in line with MCS and RECC standards
  • Support with MCS compliance. This cuts down significantly on the amount of time an installer needs to spend on paperwork and is essential should the homeowner wish to apply for the Government’s RHI scheme (annual tax-free financial support payments)
  • Mechanical and electrical drawings specific to the installation as well as clear installation manuals and customer user guides

Step 2 – Installing the product

Installing the ASHP unit is relatively simple for any plumbing & heating engineer. The heat pump controls and pipework layout are very similar to a traditional gas or oil boiler, configured as a Y or S plan industry standard layout.

  • The ASHP is simply placed on a flat concrete base external to the property with the appropriately sized flow and return heating pipes and electrical power cable running from the unit into the property
  • The electrical work should be carried out by a qualified electrician in the conventional way as you would for a gas or oil boiler

To simplify the process Nu-Heat provides a complete set of ‘as installed’ mechanical and electrical drawings, which will provide a fault-free template of the complete system layout.

Step 3 – Getting the system up and running

On completion of the first and second fix installation of the mechanical and electrical heat pump components, the ASHP unit will be ready for commissioning. It’s this element of the install that can be seen as a little daunting for a first-time ASHP installer, which is why Nu-Heat offers various levels of support:

  • Onsite commissioning. To ensure the system is MCS compliant, Nu-Heat can send out one our own field service engineers to commission and explain the system set up and functionality of the heat pump controls
  • MCS paperwork. Whether MCS or non-MCS registered, an installer can choose a support package to pass over the cumbersome compliance paperwork to Nu-Heat, freeing up time to spend out on the job and not in the office. Nu-Heat also completes and provides all of the relevant MCS support documentation for the homeowner’s RHI application, warranties and guarantees

On commissioning the installer will also receive a handover pack that is passed on to the homeowner that includes everything required for MCS compliance as well as user guides.

For more information on ASHPs, visit our heat pumps page.

A closer look at an ErP label

A closer look at an ErP label

The introduction of the Energy Related Products Directive, or ErP, means that all new heating systems will now come with a product and package label to give a clear rating of their energy efficiency. Its purpose is to make the efficiency of heating products easier to compare, helping homeowners and installers to make informed and eco-friendly decisions.

In this blog post we’re taking a closer look at an energy efficiency label for a system package. This type of label would be provided whenever a heat source such as a heat pump or boiler is paired with another add-on product, such as thermostats or solar thermal, to create what is known as a ‘package.

ErP label – an overview

You can see a breakdown of the different elements of the label on our annotated version below. Click on the image to enlarge:

ErP system label

Heat source efficiency

The top left box includes the energy efficiency rating(s) for the heat source. For a combi boiler you would see a rating for both heating and hot water. For a standard gas boiler or heat pump without a built-in water cylinder or instant hot water capability you would just see a rating for heating.

System heating rating

The top right box shows the system’s energy efficiency rating for heating.

System domestic hot water rating

The bottom right box shows the system’s energy efficiency rating for hot water. This rating is only applicable if the heat source is a combi boiler or a heat pump with a built-in water cylinder.

The extras

The bottom left box shows the optional system ‘add-ons’. These include solar thermal, a hot water storage tank, thermostats and a supplementary heater. Whenever one of the additional components is part of the overall system package, the box will be checked. These components can affect the overall heating and hot water efficiency of the system e.g. solar thermal will improve the efficiency.

» For more info on ErP, visit our ErP page.

Does a heat pump need planning permission?

Many properties will be suitable for a heat pump but it is often the plot that dictates which type of heat pump would be best suited.

Generally, to see a significant saving, a heat pump is best suited to a property that does not have any access to mains gas, as these are the properties that have the potential to benefit the most from renewables. But does the plot itself have a part to play?

Heat pump siting

Ground or air source heat pump?

A ground source heat pump (GSHP) needs space for the ground loops – the available land needs to be at least two and a half times larger than the entire floor area of the property. There also needs to be space for a plant room to hold the heat pump and cylinder. Because of this, only larger properties or those in a rural location are generally suited to a GSHP. The alternative is to drill a series of vertical boreholes that will carry the ground collector pipe.

Air source heat pumps (ASHP), on the other hand, are suitable for a wide range of property sizes and require little space. The heat pump unit sits outside and because there’s no need to dig trenches for ground loops, it is a lot quicker and easier to install. Apart from building a plinth there are no groundworks needed. This is a good option for anyone on a tight build schedule and also a smaller budget.

What about planning permission?

Permitted Development Rights permits some limited minor changes to a property without the homeowner needing to apply for planning permission.

Typically, a GSHP installation will fall under Permitted Development because the heat pump will be out of site, within a plant room. However, if the unit is being installed in a listed building or within an area of conservation then it would be worth checking the specific rules and regulations with your local council.

A large percentage of ASHP installations will also fall under Permitted Development, but the fact that ASHPs do generate some noise means that their location can be an issue, sometimes requiring Planning Permission. This ought to be checked before going ahead with the installation, just in case permission is needed beforehand.

An ASHP installation must either be classified as Permitted Development or receive Planning Permission and, to achieve Permitted Development the ASHP installation must comply with certain standards.

For more information on Permitted Development and the potential need for Planning Permission, download our information sheet.

A financial incentive

The Renewable Heat Incentive (RHI) aims to offer a real incentive to install renewable technologies, such as heat pumps, to heat homes. The scheme offers quarterly payments to homeowners over a period of 7 years, based on estimates of a household’s annual heating consumption.

In order to qualify for the RHI payments, the property and renewables system has to meet certain criteria:

  • The product itself, whether it’s a heat pump or a solar thermal system, must be MCS approved
  • The installation of the system must adhere to strict guidelines

For more information on the criteria put in place and whether the property and system are eligible for the RHI, we recommend you contact Ofgem.

You can use Nu-Heat’s heat pump selector tool to determine if a heat pump is suitable for your project.