The Guardian reader’s experience may have been due to improper installation or the use of older, noisier heat pump models, according to Jack Harvie-Clark, a director at Apex Acoustics. “Modern heat pumps can be significantly quieter, and proper placement – away from property boundaries – can further reduce noise impact,” he said. Apex was one of the consultancies behind the report cited by the Telegraph. It was quick to rebuff the coverage, describing its “misleading” claims that heat pumps were too noisy for millions of UK homes as “an exaggeration”. “While noise is a valid concern … technology improvements and proper installation can mitigate noise issues in most homes. The article presents noise as an insurmountable problem, which is not the case,” the company said, pointing out that there were many homes – typically detached and semi-detached properties – where there would be no problem at all. Last November the UK government published the results of its review, which found that noise emissions were a concern for a minority of consumers, with a low incidence of complaints. In the chancellor’s autumn statement later that month, it was announced that the government would consult on changing rules that apply in England, including removing the one-metre boundary rule. The government’s research included a survey of households living within 50 metres of a heat pump, across 60 areas with high heat pump uptake, to gauge noise nuisance inside the house. It asked respondents to specify which neighbourhood noises could be heard from indoors. Heat pumps received one of the lowest number of mentions, while dogs topped the list. The study found that 57% of the 139 respondents noticed barking during the day, and just 4% noticed the sound of a heat pump. Harvie-Clark has done further research on the issue for Nesta, an innovation charity, which is due to be published this month. Its findings suggest that even in worst-case scenarios with high housing density and all air source heat pumps operating simultaneously at maximum permitted sound power levels, the cumulative noise impact was not likely to be more significant than the individual noise impact of the nearest neighbour’s heat pump. “I’ve also investigated in detail how some other European countries manage noise from air source heat pumps,” Harvie-Clark said. “Most have higher noise limits in the daytime and some, but not all, have slightly lower limits in the night-time. “We [in the UK] have one noise level limit for all times, which to me seems clumsy. The main manufacturers see northern Europe as one market, so they all have controls that can limit operation to lower noise levels at night-time The caveats Although potential noise issues can be mitigated, Harvie-Clark believes that more work should be done to understand the impact of heat pumps as they gain popularity across Europe, and he has stressed that consumer education is key to ensuring that the right heat pump is installed in the right way. For example, the government’s review of whether heat pump noise is noticeable has some notable limitations: heat pumps are not widely used, so even an area of “high density” will include fewer heat pumps than there will be in the future. There are other issues with the way noise limits are characterised. For example, a heat pump’s defrost cycle, which is louder than its normal running level, is not included in MCS’s noise tests. “Nor is low-frequency noise, nor any information on tonality or directionality,” said Harvie-Clark. “So these things cannot by definition be taken into account in any calculation or assessment prior to installation.” The verdict Heat pumps are quieter than they used to be, and getting quieter still. But better consumer information could go further in mitigating the overall impact of noise by choosing the best model for the home and using it correctly. “I believe that many people in the UK try to operate their heat pumps the way they operate gas boilers – turning them on and off – but they can’t heat houses as quickly as gas boilers, so they need to run constantly to do that,” said Harvie-Clark. Turning heat pumps on after a period of being off will require the machine to work harder and therefore create more noise. So taking a slow and steady approach to home heating can make heat pumps more efficient, and quieter, too. “In colder European countries they accept that this is how to run heating systems. Our temperate climate means people have different control expectations,” Harvie-Clark said. “While the potential noise impact of air source heat pumps should be considered, it is important to balance this with the significant environmental benefits of transitioning away from fossil fuel heating systems. Gas boilers also make a noise.”