Heat pumps used to be something you’d only hear your tech-savvy neighbor talk about. But in the last two years, it seems like manufacturers have been announcing a newer, more capable, more appealing model every month. Many claim that their cold-climate heat pump models can heat homes with full capacity at temperatures as low as 5° Fahrenheit (F) (–15° Celsius [C]). And a number make that claim at even colder temperatures. On paper, heat pumps are ready for prime time. So what’s holding everyone back?