Size vehicle A/C by cabin volume, solar load, occupants and ambient temp.
| 车型 | 车室容积 | 典型制冷量 | 折合匹数 |
|---|---|---|---|
| 微型车 | 约 3 m³ | 1.8 ~ 2.4 kW | 约 0.7 ~ 1.0 匹 |
| 轿车 | 约 4 ~ 6 m³ | 2.4 ~ 3.6 kW | 约 1.0 ~ 1.4 匹 |
| SUV / MPV | 约 6 ~ 9 m³ | 3.5 ~ 5.5 kW | 约 1.4 ~ 2.2 匹 |
| 轻客 / 房车 | 9 ~ 20 m³ | 5.5 ~ 12 kW | 约 2.2 ~ 4.8 匹 |
总冷负荷 = 车体传热（与容积、温差、隔热相关）＋ 乘员散热（每人约 0.1~0.15 kW）＋ 日照辐射＋ 新风负荷。容积只是基础项，正午暴晒与满载人员会显著抬高需求。
车载空调长期处于振动、高温与变转速工况，COP 低于家用机。选压缩机时建议按计算冷负荷留 15%~25% 余量，并同步核对冷凝器散热面积；「小马拉大车」会导致高温天长时间不停机却不降温。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Cooling capacity | capacity must cover cabin load from conduction solar and occupant heat | ISO 13043:2011, refrigerant R134a |
| Refrigerant safety | charging and service follow safety rules against high pressure release | SAE J639, refrigerant safety |
| Efficiency impact | air conditioning load affects fuel use so compressor size should avoid part load | UN GTR 15, worldwide harmonised test cycle |