Air-source heat pumps extract heat from outdoor air. At sea level, a unit rated at 36,000 BTU delivers close to that figure in real conditions. At Aurora’s elevation, reduced air density means the same unit moves less heat per cycle. Without an altitude-derating adjustment in the load calculation, the system is effectively undersized from day one, it runs longer, works harder, and rarely hits its rated SEER. The fix is straightforward: the load calculation has to account for elevation before any equipment is selected.
Mini-split systems face the same altitude constraint, with an added layer: each indoor head must be sized to the BTU load of its specific room, not the whole home. An oversized head short-cycles, leaving humidity high and temperature uneven. An undersized one runs continuously without reaching setpoint. We arrange a room-by-room load calculation before any equipment is recommended, so each zone is matched to its actual demand rather than a rough square-footage estimate.
Geothermal systems sidestep the air-density problem entirely by drawing heat from stable ground temperatures below the frost line, typically 50-55 degrees Fahrenheit at Aurora’s depth. That consistency means rated BTU output holds regardless of how cold the outdoor air gets. The trade-off is a more involved site assessment: loop type, soil conductivity, and available lot area all affect system sizing. We arrange that assessment and produce a written estimate covering loop design, equipment, and installation scope before any ground is broken.