They hang off the walls of utility rooms, nestle inside kitchen cupboards and hunker down in cellars. Gas and oil boilers and furnaces have been making homes more comfortable for decades. Their adoption during the 20th century heralded the dawn of central heating and on-demand hot water and put an end to the days of shovelling coal. But if the goal of decarbonisation is to be met, these boilers must go.

Thirteen European countries plan to phase fossil fuels out of building heating, and air-source heat pumps have emerged as the best alternative. These extract ambient heat from the outside air, even when the temperature is below freezing, and concentrate it to warm inside spaces. Heat pumps are far more efficient than boilers, in terms of the amount of energy used per unit of heat generated.

Lately, however, they have become a symbol of the obstacles that await as countries try to decarbonise. Until recently, green policies had seldom required private citizens to roll up their sleeves and make big disruptive, changes to their lives. Now, they are starting to, and many people do not like it.

The annoying thing about heat pumps is that you cannot simply swap a gas boiler out for a pump—at least not yet. Heat pumps are larger than gas boilers, require outside space and, for the 60% of European properties that are old and leaky, their installation must be accompanied by additional insulation.

In Britain knowing whom to trust on the best green heating design for your home is hard enough to discourage all but the most determined and wealthy eco-warriors. Owners of older houses face difficult choices like lifting up all their floorboards and lining their inside walls with thick insulation, or wrapping their homes in a much thicker layer of external insulation, which may not be allowed by local planning rules. All this can quickly become costly, disruptive—and politically toxic. A plan in Germany to ban gas- and oil-boiler installations as early as next year, for instance, was abandoned after a public outcry.

What to do? Although heat pumps that are an easy swap for boilers are eventually likely to come on to the market, households cannot even then be entirely spared from disruption. The least governments can do is make adoption as easy as possible. Although grants are available in some countries, their administration is often sluggish and should be sped up. A target cannot be enforced if there are not enough skilled workers to retrofit homes; they will need to be trained. The clash between planning regulations and green rules, which makes householders feel helpless, must be resolved.

Germany’s watered-down rules, which are due to be passed in parliament later this week, wisely give households more time, and also ask local authorities to be involved in their administration. They will give large and small municipalities until 2026 or 2028, respectively, to draw up transition plans, which can allow for greener heating that does not involve heat pumps. Municipalities know their local housing stock better than central governments do, and they make the planning decisions that often clash with the demands of retrofitting. They must start favouring the planet more and nimbys less.

This episode contains a lesson for governments. Decarbonisation on the scale required to avert planetary calamity will be painful. Voters will often object; and may sometimes sack green-friendly governments. So it is crucial that policies are designed to reduce emissions as efficiently as possible, with incentives designed wherever possible to persuade rather than coerce. Even with the best-crafted policies, however, there will be more backlashes. Governments must prepare. ■