A heat pump isn’t nearly as sexy as an electric BMW or a floating wind turbine. But on an individual level, it might make a big difference.

Flowers grow next to a heat pump at a residential house.

Flowers grow next to a heat pump installed at a residential house. (Photo by one pony/Getty Images)

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In the race to achieve net-zero greenhouse emissions in Europe, keeping older homes warm in winter without relying on natural gas is not easy. But a new generation of air-source heat pumps could be the answer.

New types of the refrigerants that power heat pumps, such as propane or carbon dioxide (CO2), may overcome many of the obstacles to installing them in ageing buildings.

Russia’s full-scale invasion of Ukraine in 2022 brought home Europe’s dependence on Russian gas, triggered massive price rises for fossil-fuels and spurred rapid growth in wind and solar energy that are seen as vital in the battle against catastrophic global warming.

According to Marek Miara, an expert in the technology, in Germany heat pumps will likely become the dominant heating technology for residential buildings.

Heat pumps work like refrigerators in reverse, taking in ambient heat from the atmosphere, concentrating it and piping it into a building. For every unit of electricity used by the heat pump, it can deliver up to five times as much energy as heat. In comparison, a gas boiler can only reach about 90% efficiency.

Staying warm while cooling the atmosphere

Heat pumps can work in temperatures down to -25C, as proven in Scandinavia where heat pumps have been used in bulk for a decade and Finland tops the European league for the number installed as a proportion of its population. In southern Europe air-to-air systems, like conventional air conditioners, can provide cooling in the summer and heating when needed.

Why does this matter?

Buildings across Europe account for 12% of greenhouse-gas emissions. In Great Britain, that number rises to 14%, thanks to the country’s strong reliance on gas heating for nearly three-quarters of homes.

Getting those numbers down are central to Europe’s target of reaching net-zero emissions by at least 2050 along with decarbonising power generation and switching wholesale from petrol and diesel cars and trucks to electric vehicles.

In some countries renewable energy from a combination of wind, solar, hydroelectric or nuclear already produce well over half the electricity. The European Union has raised its binding renewables target for 2030 to 42.5%, which is almost double the existing share across its 27 member nations.

The switch from gas

Replacing gas-fired boilers for heating buildings is more difficult, however, in countries like Britain and the Netherlands, which share a high proportion of homes heated by gas. Britain also has some of the worst insulated and draughty homes in Europe with many dating back many decades.

Until recently heat pumps have heated the water used to run heating systems to a lower temperature than gas boilers, meaning they worked best in homes with high levels of insulation. Retrofitting older properties often meant expensive work to improve insulation and install bigger radiators or underfloor heating.

Heat pumps are also much more expensive than gas boilers despite subsidies and have run into political headwinds in Germany and Britain.

In Britain, the ruling Conservative Party decided last year that watering down targets for heat pumps and the phasing out of fossil-fuelled cars might give it a useful culture-war edge in a national election due this year.

In Germany, a backlash promoted by the far-right Alternative for Germany party, has forced the coalition government to water down regulations that would have outlawed the installation of most new gas-fired boilers from this year.

Climate-friendly refrigerants

The Fraunhofer Institute for Solar Energy Systems in Freiburg, Germany says it has successfully tested using propane as a natural refrigerant that is cost effective, climate friendly and, crucially, can generate heat at a similar temperature to gas-fuelled boilers.

Although propane is highly flammable, it has a small impact on global warming in comparison with F-gases or fluorinated greenhouse gases — potent climate-changing refrigerants that are being phased out under EU regulation.

That means precautions must be taken currently to ensure propane heat pumps remain safe, but the institute has developed a system that uses less than 150 grams (5.3 ounces) of propane. That is the limit in Germany for installing a unit inside a building without extensive safety precautions.

In a statement for the Fraunhofer Institute, heat pump expert Lena Schnabel said said that the goal was to develop a heat pump module which uses propane, provides sufficient heat for single-family homes and doesn’t exceed the 150-gram limit for indoor use. “We have now achieved this goal in cooperation with our industry partners and have given them the tools to develop a market-ready heat pump,” Schnabel said.

Fraunhofer researchers led by Schnabel are now working on propane-based high temperature heat pumps that could be fitted in flats and multi-family houses where up to now it has been difficult to instal such units because of a lack of outdoor space.

Using carbon to reduce carbon emissions

Another natural refrigerant is carbon dioxide, the greenhouse gas that is a major cause of climate change. Swedish heat pump manufacturer Vattenfall launched a CO2 heat pump in the Netherlands in 2022 that it said can generate heat at the higher temperatures needed for a direct swap with conventional gas boilers without costly retrofitting.

Company spokeswomen Emily Faull-Jones said the company had successfully installed its CO2 heat pumps for housing associations in the Netherlands and was planning to roll it out to individual homeowners. It has yet to be introduced into the UK.

From a low base, Britain has seen a rapid rise in renewable energy installations, with 35,000 heat pumps installed last year. That is way below the target set by the government for 600,000 installations a year by 2028, however.

A big boost came from the government raising the grant it offers for heat pump installations to as much as £7,500 — an increase of around £2,500 or $3,200.

British numbers are puny in comparison with the rest of Europe. The European Heat Pump Association, a trade group, said three million units were sold across 21 European nations in 2022, which was a 39% rise on the year before. France installed the most units, but in terms of the numbers sold per 1,000 householders Finland led the pack.

One big problem is a shortage of engineers qualified to install heat pumps. Across Europe there is a shortage of trained engineers, which is a serious impediment to rolling out energy-saving systems. Many countries are working to increase the number of engineers, but that takes time.

Despite that, Thomas Nowak, secretary-general of the European Heat Pump Association, is optimistic.

“The foundation is laid for continued exceptional growth and with it the benefits heat pumps bring in terms of climate action, energy independence and jobs,” Nowak said. “This is without a doubt the decade of heat pumps.”

Questions to consider:

  1. What stands in the way of greater use of heat pumps?
  2. Can advances in the refrigeration gases used in pumps win over sceptics?
  3. Why are heat pumps becoming a target in “culture war” political battles?

Malcolm Davidson worked for four decades as a journalist in Europe, Asia and Australasia. He served as correspondent with Reuters in India, Pakistan, Afghanistan and the Philippines, and reported widely from other parts of Asia. He also worked in Brussels and most recently was the London-based editor of Reuters’s Front Page multimedia news service.

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