Myth Busting alongside The Guardian

The Guardian recently ran an article titled “Are heat pumps the future or just a lot of hot air?”

And in fairness to the Guardian, they were very positive about heat pumps and helped to dispel a few myths.

However, as the heat pump experts, we’re going to go one step further and end the myths.

Myth 1 – Heat Pumps are more expensive to run than gas boilers

Myth Busting – Heat Pumps are NOT expensive to run

Despite the cost per unit (kWh) of electricity being 4 times more than that of a kWh of gas, this is offset by the superior efficiency of a heat pump. A modern, well-maintained gas boiler will typically achieve an 80-90% efficiency, making the cost per unit of heat generated, approximately 6.9-7.8p/kWh. In comparison, a modern air source heat pump will achieve an average efficiency (seasonal co-efficient of performance) of 3.7, or 370%. The cost of generating 1kWh of heat via an air source heat pump is therefore approx. 6.62p. Ground source heat pumps in comparison, will typically achieve a 400% efficiency, making the cost of heat generation – per unit, even less.

Please note – these figures are based on current UK tariffs as of 1st October 2024.

Myth 2 – Heat Pumps don’t work at freezing temperatures

Myth Busting – Heat Pumps DO work in freezing temperatures (just ask Norway)

The refrigerant within modern air source heat pumps (typically R32 or R290) have a boiler point of less than -30’C. The evaporation (boiling) of the refrigerant is the first part of the process that makes a heat pump operate. As such, even during the very coldest days in the UK, where outside air temperature plummets to -5’C, there is still plenty of energy within the air for the refrigerant to boil/evaporate, making the heat pump work.

Ground temperature, however, remains relatively constant year-round – beyond a few feet below ground level. This tends to be around 10’C, which again, provides plenty of energy to make a ground source heat pump operate effectively and efficiently.

Myth 3 – Heat Pumps cannot be installed in older properties

Myth Busting – Older properties are PERFECT for Heat Pumps (just ask one of our 100’s of customers over the past few years)

In our 18 years of installing heat pump systems, we have encountered every type of building, from highly efficient new builds, to period farmhouses, and mid-1900’s townhouses to stately homes. Every house or building, regardless of its complexity, age, or efficiency, is a box. Each box loses heat – some more than others – the older/less thermally efficient the box, the higher the rate of heat loss. Providing the heat pump is capable of supplying more heat than the house loses at the design conditions, the house/building will be warm. Clearly there’s an added layer to this in that the individual room distribution also needs to be appropriately sized.

Despite older properties being less thermally efficient than new houses, they do tend to have one advantage, and that’s greater thermal mass. A heat pump system applies a steady-state heating strategy as opposed to a boiler which tends to operate intermittently. When applying steady state heating, not only does the internal air within the house become warm, but so does the building fabric. A house with greater thermal mass has a greater ability to store heat, and thus will eventually begin to act as a ‘heat sink’. Owners of old houses will testify to his, as those with large thermal mass will experience cooler indoor temperatures for the first few days of a hot spell during summer. This is because the building fabric absorbs the heat before it begins to emit it into the rooms. Modern, lightweight constructions in contrast, have low thermal mass, and therefore will become very warm, very quickly in summer.

Myth 4 – I will need to spend a lot insulating my home

Myth Busting – False, you will NOT need to spend lots insulating your home

Whilst the application of insulation will lead to improved thermal efficiency, and therefore reduced heating bills, the cost and disruption of doing so needs to be considered as part of the wider project. Clearly in the case of a heavy renovation project, there is value in considering the options for retrofit insulation, but not everyone wants to have their house re-plumbed, re-wired, and re-plastered in order to accommodate internal wall insulation – as an example. With experts in energy assessment and retrofit, we are able to discuss the options surrounding insulation, including the benefits, potential drawbacks, and practicalities.

Traditional properties were not built to be air-tight, instead, they were designed to be permeable, with the ability to absorb moisture. We’re not therefore in the game of recommending every house and building is wrapped in an insulated blanket. Instead, we aim to assess and consider the nature of each property, make practical recommendations where we deem it appropriate, and provide a heat pump specification to suit – whether the customer chooses to make the insulation upgrades or not.

We do however think there is merit in grabbing the ‘low hanging fruit’. This can often be in the form of upgraded loft insulation, or retrofit cavity wall insulation, as they tend to be relatively low cost and low disruption. The cost of doing so is often offset within the heat pump project, as it can reduce the size/number of heat pumps/radiators required. Heating bills will also be reduced because of the insulation upgrades (aside from the heat pump installation) thereby further improving the ROI.

Myth 5 – My Heat Pump might be a noise nuisance to neighbours

Myth Busting – Heat Pumps are NOT noisy

One of the major developments in air source heat pumps over the past 5 years (aside from far greater efficiencies) is reduced noise levels. Modern air source heat pumps are typically quieter than a boiler flue. That aside, as part of our MCS obligation, we have to carry out a permitted development noise assessment to MCS 020 standard. This considers the sound power level of the proposed heat pump, the distance from the nearest neighbour – and specially, a window to a habitable room, and whether there are any barriers between the proposed heat pump position and the assessment position. Should the proposed installation fail this noise assessment, either an alternative location will be sought, or a full planning application will be made.

It is also worth noting that the time of year when your neighbours are likely to spend most time in their garden (ie. summer) the heat pump will only be providing hot water, and therefore will only operate for short periods, now and then.

Ground source heat pumps in contrast, are typically installed within the house, garage, or plant shed, and are typically no noisier than a fridge/freezer.

Myth 6 – Heat Pumps could cause blackouts

Myth Busting – Regulations ensure Heat Pumps WON’T cause blackouts

Prior to any heat pump installation, and therefore prior to making a connection to the customers mains electricity supply, Finn Geotherm will complete a DNO (Distribution Network Operator) application. This will declare the maximum electrical load of the proposed heat pump system. The incumbent DNO will then assess this against the customers local supply (via their unique Meter Point Administration Number) as well as the impact on the wider network infrastructure. Should the proposed installation pass these checks, the installation can proceed.

However, if it exceeds the level of spare capacity within the customers supply, this may result in the requirement for an upgraded supply to the property. Equally, should the application fail on the network checks, this could result in upgrades to the wider infrastructure being necessary. Whilst network upgrades formerly came at a cost to the applicant/homeowner, newly available funding means the majority of these costs are now covered by the Distribution Network Operators.

This ultimately means that Finn Geotherm will never complete an installation that risks negative impact on the local/wider network.