Data source: Koven measured COP ladder (first-party, bench + field on production units; return air 21 °C/70 °F): +7 °C = 4.0–4.2, 0 °C = 3.5–3.7, −5 °C = 3.0–3.2, −10 °C = 2.7–3.0, −12 °C = 2.5–2.8, −15 °C = 2.3–2.5, −18 °C = 1.7–2.1, −20 °C = 1.6–2.0, operational to −30 °C via EVI vapor injection. COP declines with temperature — that is physics; values between points are interpolated. A true cold-climate unit stays useful far below the 0 °F default lockout that NREL models for standard heat pumps.