By 2045, according to the Scottish Government's Heat in Buildings consultation, "polluting" heating systems will be banned, and all homes will have as their mean heating, "clean systems". This means, for the most part, that the majority of homes will either have their own heat pump or be connected up to a district heating network.
A massive proportion of Scotland's greenhouse gas emissions come from heating our homes, with domestic buildings accounting for around 13% of Scotland's emissions. Non-domestic buildings account for around 7%.
Hence, Scotland cannot honour its commitments to mitigating climate change without a wholesale transformation in how we heat our homes, and a shift away from a predominantly fossil-fuel,-based system of heating.
How much does an air-source heat pump really cost to install?
An Institute for Public Policy Research report estimates that the upfront cost of retrofitting homes in Scotland falls largely in the range of £10,000 to £15,000 per home, though other sources suggest some can reach £30,000. A Scottish Government grant of £7,500 therefore only covers part of this.
A problematic issue is that costs are similar across the income spectrum. Just because you have a smaller home, doesn't mean it will be much cheaper - and this, the IPPR report says, means that “if no policy were in place to share costs, the transition would have a deeply regressive impact, costing poorer households a much larger proportion of their income than richer households.”
A ground source heat pump can cost between £18,000 and £25,000 to install, making them unaffordable for all but wealthier individuals, though networked ground source heat pumps are being developed that could service whole streets or blocks.
But what do the costs look like for real home retrofits. Here is one, for instance from Neil Kitching, who not only had a heat pump installed in his Dunblane home, but also solar PV, battery storage and underfloor insulation.
What government-funded grants and loans are available for heat pump and energy efficiency measures?
Through Home Energy Scotland homeowners can get a grant of up to £7500 for installing new heat pumps. Those in rural areas may qualify for rural uplift and a maximum grant of £9000. There is also grant funding for energy efficiency improvements, up to a maximum of £7,500 (£9000 for those qualifying for rural uplift). Also available is an additional £7,500 interest-free loan.
Read more: Heat pumps: Myths, truths and costs – find all articles here
Producing heat from cold air seems like magic. How does a heat pump work?
It’s often said that a heat pump functions a bit like a “fridge in reverse”. Heat is transferred from the outside into the building’s heating system, using a mechanism that involves a combination of evaporation and condensation. Retired physics teacher, Pat Hackett, explains just how that magic works.
Can a heat pump really make 1kW of electricity into 3kW of heat?
It can, and does so by drawing the rest of the heat energy from the air, even when it seems cold. That conversion ratio is called its coefficient of performance (COP). A system in which 1kW is converted to 3kW would have a COP of 3, or 300%. It’s often said that a standard coefficient is about 3, but some rare systems have reached as high as 5.
According to an Energy Savings Catapult study of 750 homes, the median seasonal coefficient of performance (SCOP) over the whole year was 2.8 (280%). An older, 2021 analysis, found it to be closer to 2.7 for air source heat pumps.
What does this mean for heat pump bills compared with gas?
The relative efficiencies of gas boilers (average 85%) and air-source heat pumps (average 290%), along with relative costs of energy - with electricity four times that of gas - are what determine the impact on bills.
Dr Jan Rosenow of the Regulatory Assistance Project (RAP), writing in Carbon Brief, noted that at a SCOP of 2.9, the “yearly heating costs to run a heat pump on the current standard tariff would be £25 higher than an 85% gas boiler”.
This means, taking Energy Systems Catapult's 2.8 median SCOP, that at least half of heat pump users are paying more on their bills, but slightly less than half are paying around the same or less. Someone with a SCOP of 4, he said “would save 25% on their heating bills compared with an 85% gas boiler”.”
- Can you fit a heat pump in an old Glasgow tenement flat?
- Heat pump Scotland. Maps, graphs and missing targets
- How noisy are heat pumps? We put them to a sound meter test
What else could bring down heat pump bills?
Many heat pump users combine with solar and battery combinations to bring down bills, but also seek out the best tariffs and time their use of electricity.
The biggest factor that could bring down energy bills for heat pump homes is a drop in the cost of electricity. Robin Parker, a mission manager at the innovation foundation Nesta said: “One of the most significant changes which would make it easier and cheaper for people to run greener, electrically-powered heating at home would be for the UK Government to bring down the high cost of electricity compared to gas. This ratio between electricity and gas prices is one of the worst anywhere in Europe.”
Will I be made to install a heat pump?
Included in the recent Heat in Buildings bill consultation are various mechanisms to put pressure on homeowners to switch to zero-emissions heating.
Amongst them is a trigger at the time of the sale of a property, after which the purchaser will have two to five years to make the change. It's also planned that if a local heat network becomes available, the homeowner will be required to join it or switch to another clean energy system.
How much insulation do you really need before getting a heat pump?
This matter is hotly debated, but increasingly experts are arguing that homes do not have to spend huge amounts of money maxing out on insulation.
A Nesta report said: “It is often claimed that the UK’s housing stock needs to be much better insulated before heat pumps can be installed. This is largely untrue. Insulating homes is generally a good thing – it saves energy, makes homes healthier and more comfortable, can ease pressure on the electricity grid – but it is not essential for switching homes to heat pumps.
"If the aim is to reduce carbon emissions as quickly as possible with a limited budget, then adopting heat pumps typically provides greater carbon savings per pound spent than insulation measure.”
Is Scotland too cold for an air-source heat pump?
Despite the fact that heat pumps are common and popular in cold Scandinavian countries, and European countries with the lowest temperature winters have the highest heat pump sales, there is a prevailing belief that Scotland is too chilly for this technology. The research, however, suggests that we are not.
Energy Systems Catapult, which has monitored heat pump performance in its study of 750 homes, says: “Critics of heat pumps will be quick to say that they do not work in cold weather conditions. This is simply untrue. At times, the recorded external temperature fell to below -10°C, and yet the heat pumps continued to keep homes warm, exhibiting efficiencies of 200% on average.
A paper by the Regulatory Assistance Project (RAP), which looked at research from studies across Europe and North America, found that heat pumps outperform oil and gas heating, even at temperatures near -30°C.
What is the biggest thing I can do to improve the energy efficiency of my home?
“Insulation,” says Sophia Bates programme manager at Home Energy Scotland, “makes the biggest difference in terms of energy efficiency, though what insulation that is depends on the kind of home you’re in. A detached home that has air around four walls, will see much bigger difference from wall insulation than a terraced home that only has front and back to the air. We try to encourage people to have a whole house approach.”
Tools on the Home Energy Scotland website help homeowners get ain insight into what combination of measures is likely to have the biggest impact and value for money.
“In terms of the quick no regret solutions that have a positive impact," she said, "the real obvious ones are loft insulation, cavity-wall insulation (if there are cavity walls), and draught-proofing.”
Will you need to replace your radiators and get underfloor heating?
Like getting good insulation, putting in new, bigger radiators more suited for the heat pump system, replacing piping and installing underfloor heating, is not absolutely essential but does make a difference to performance.
Increasingly, however, the market is seeing more otter heat pump models that would more easily fit directly onto current heating systems - though these tend not to achieve such high efficiencies. For instance, Octopus recently launched its Cosy 6, which runs at temperatures of 78-80°C and could be fitted to existing radiator and hot water systems.
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