How the check works
Condensus mathEach system's "heats down to" figure is the lowest outdoor temperature its maker says the heat pump keeps running at (for example 5°F for many standard systems, -13°F to -22°F for hyper-heat models). A system is listed for your temperature when that figure is at or below it.
LimitsRunning is not the same as full output: most heat pumps deliver noticeably less heat near their limit, so homes that often see those temperatures usually keep a backup heat source. Systems that don't state a limit are listed separately rather than guessed.
Questions
What is a hyper-heat or cold-climate mini-split?
Makers use these names for systems with enhanced compressors that keep heating at very low outdoor temperatures, typically -13°F to -22°F, and hold more of their capacity at 5°F than standard models.
Where do I find my design temperature?
Your local building department or an installer can give it; it is also published in ACCA Manual J and ASHRAE climate tables. It is usually well above the record low.