In countries experiencing cold snaps, heating is a hot topic. What should one do when a boiler shrugs off its mortal coil? Rush to replace it? Or is it time to switch to a heat pump?

That is a crucial question for households looking to save money on energy bills, and also for governments. In the UK, for example, 28mn homes together account for roughly 15 per cent of the country’s emissions.

For the typical household, money will be the deciding factor. And if carbon were no issue, the boiler would still be the cheapest way to go, at least in many cases. The upfront investment is significantly lower — some ￡3,000 compared with maybe ￡8,000 for a heat pump, even including a hefty government subsidy. The latter may also require more insulation and the installation of bigger radiators or underfloor heating.