For years, heat pumps were seen as the fragile heroes of mild climates, efficient in theory but unreliable when the mercury dropped. That narrative has now collapsed under the weight of experience.

An international research group led by Slovenia’s University of Ljubljana has conducted a review of emerging ultra-high-temperature heat-pump technologies based on solids or gases. All of those ...

Heat pumps can reduce carbon emissions associated with heating buildings, and many states have set aggressive targets to increase their use in the coming decades. But while heat pumps are often ...