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. From the frozen lakes of Finland to the prairies of Canada, heat pumps are thriving where they were once thought impossible. The data from the multiple past winters tells the story clearly. Even in subzero temperatures, installations are growing faster than almost any other clean heating technology. This shift is more than a technical achievement; it…