What to expect when you switch to a heat pump to heat your home

Heat pumps are growing in popularity as an efficient and low carbon way to heat our homes – but what’s it really like to have one working in your home? Let’s find out.

Heat pumps are an efficient and low carbon method of heating (and provide cooling in the summer too), so they’re a great option if you’re looking to replace a fossil fuel heating system in your home. At the moment, heat pumps also have the added bonus of being eligible for payment under the Renewable Heat Incentive (RHI) scheme, so it’s likely also a financially savvy change to make for your home.

But, heat pumps are also still relatively rare in homes. We come across lots of questions from homeowners who are considering getting a heat pump but aren’t sure what to expect from a heat pump. In this post we cover some of those questions.

How much space will it take up?

Most heat pumps (ground source, air source, or water source) used for home heating will be 4 and 15 kW in output, depending on the size of the home and how much heat is lost in the home. Always make sure you’re working with a trusted MCS certified heat pump installer (like those we work with at Cosy Homes Oxfordshire) as they’ll be able to accurately determine the size of heat pump you need.

In terms of translating this into the space needed in the home, it depends on the type of heat pump you’re hoping to install.

Ground source heat pumps use heat from the ground and so need to be installed underground. This means that you will need a substantial amount of outdoor space, and installation will result in your garden being dug up. There is sometimes the option to use bore holes instead, installing the heat pump vertically rather than horizontally, which takes up less space.

Air source heat pumps require less space, with an external unit which is around the size of washing machine. These are usually wall-mounted, so you will need enough space on one of your outside walls to install this.

If you are using a heat pump for your hot water as well as your heating, you may also need a new hot water cylinder inside your home which is designed for heat pumps, so you’ll need to consider the space for this too.

How noisy are heat pumps?

An air source heat pump uses a fan to take in air to use its natural warmth, which does create some noise. However, this noise is outside your home, and usually you won’t hear anything from inside the home – and neither will your neighbours!

Will I notice that the system is cooler than a traditional gas or oil boiler?

Unlike gas and oil boilers, heat pumps deliver heat at lower temperatures over much longer periods. For instance, if you are using a heat pump to provide hot water, it will normally reach a maximum of 55°C, compared to a gas boiler which can reach around 20°C more than this.

This can be difficult for some homeowners to get used to. We’ve grown up with radiators and showers that get scalding hot, and see that as an indication of heating and hot water working effectively.

But, the reality is that you don’t need your radiators or showers to be that hot – a 55°C shower would still leave you with burns! And because the heat pump delivers a more constant temperature than a typical gas boiler (which you’re often turning up or down to try and reach an optimal temperature) you’ll still be at a comfortable temperature – often much more comfortable because of the consistency – even though the radiator does not seem properly hot to the touch.

It’s just a change to get used to, and we find that most homeowners get used to this fairly quickly and enjoy a more comfortable, constant temperature across their home.

Will I need to do other work as well as installing the heat pump?

It isn’t always as simple as a direct replacement of your existing gas or oil boiler with a heat pump. Heat pumps are most effective and efficient when they can operate at a lower temperature. In order to enable this, we always advise homeowners to reduce heat loss from their home before installing a heat pump – and this is why we always start our process with a home assessment and Whole House Plan, to check the situation of the entire house before diving into one particular solution.

If you do need to reduce heat loss first, this typically involves adding or increasing insulation (floor, loft, and/or wall) and draught-proofing or repairing window glazing. If your home is already airtight and efficient, though, you may be able to skip this step.

If you are using an air-to-water heat pump, you may also need to replace your hot water cylinder and radiators to ensure the heat pump can work. Heat pumps work best with underfloor heating, so this may be needed, but some radiators will also work fine.

How much will I save on my bills?

If you’re hoping to save money on your energy bills through installing a heat pump, it may not actually be the best option for you – for us, it’s all about the carbon impact.

Heat pumps will likely save you money if you’re switching from an old electric storage heater, as heat pumps are powered by electricity and will use significantly less than your old heaters.

However, if you’re switching from a gas boiler (which most homes in the UK will be) then your bills may actually increase. This is because gas is currently much cheaper than electricity. However, if you’re also reducing heat loss and improving the energy efficiency of your home at the same time (through e.g. insulation and draught-proofing) then you likely will save money on energy bills after installing the heat pump, as you’ll be wasting much less energy.

At the moment, in the UK you can also receive payments from the government after installing a heat pump, through the Renewable Heat Incentive (RHI). You can expect this to give you an added income of £900-1400 per year.

Are the controls complicated?

Heat pumps typically have heating controls and thermostats. They usually aren’t anymore complicated than the controls you’d find on a typical boiler, but they may be different to what you’re used to, and you’ll need to get used to the best way to programme the heat pump to be most efficient (usually having the heating on for a long time at a low setting). If you use a trusted MCS installer, they’ll always explain how to use your new heat pump and be there to support you if you have any teething problems.

Is legionnaires disease something I should be concerned about?

Legionella is a type of bacteria that grows in warm waters and can cause legionnaires disease in humans – causing headaches, coughs, and even pneumonia. Legionella is killed at temperatures above 60°C, so is not an issue with standard boiler systems but is something that needs to be considered with heat pumps as they typically reach around 50-55°C.

The answer is to raise the temperature of the heat pump above 60°C once a week. Typically this is done using an immersion heater, which most cylinders come with as standard, and this will be programmed during install. If you’re not sure, make sure you check with your MCS certified installer, and they’ll be able to answer any questions about your particular heat pump system.

Want to hear a homeowner’s experience?

We have two Cosy Homes Oxfordshire case studies involving the installation of a heat pump as a low carbon heating system – one an end terrace house in east Oxford and one a cottage in the village of Hook Norton.