Heat Pump Sizing Calculator for California Climate Zones
Estimate the required heat pump capacity for your California home using Manual J-based load factors adjusted for each of California's 16 climate zones. Enter your home's details below to get a recommended BTU/hr and tonnage.
Formulas Used
Cooling Load (Sensible):
Q_cool = (A_wall × U_wall + A_ceil × U_ceil + A_floor × U_floor × 0.5 + A_win × U_win) × ΔT_cool + A_win × SHGC × I_solar × 0.5 + V × ACH × 0.018 × ΔT_cool + 250 × occupants + 1.5 × A_floor + 1.0 × A_floor
Total Cooling Load (with latent): Q_cool_total = Q_cool_sensible × HumidityFactor
Heating Load:
Q_heat = (A_wall × U_wall + A_ceil × U_ceil + A_floor × U_floor + A_win × U_win) × ΔT_heat + V × ACH × 0.018 × ΔT_heat
Recommended Capacity: Q_design = max(Q_cool_total, Q_heat) × 1.15
Tonnage: Tons = Q_design ÷ 12,000 BTU/hr/ton → rounded up to nearest standard size
Where: ΔT = design temperature difference (°F), U = overall heat transfer coefficient (BTU/hr·ft²·°F), ACH = air changes per hour, I_solar = 180 BTU/hr·ft² (CA average peak solar intensity), SHGC = solar heat gain coefficient.