负荷计算的目的是为了合理地选择导线截面，确保电气线路和设备经济、安全地运行。常用计算负荷的方法中有“需要系数”法，该法较简单、精确度较高，且是实用的工程计算方法，因而得到广泛的应用。
　　一、电器负荷的计算
　　确定了各用电设备容量之后，将各用电设备分类，即将感性负荷与纯阻性负荷分类。现在民宅中的感性负荷主要有洗衣机、空调器、电冰箱、电风扇、荧光灯中的电感性镇流器；纯阻性负荷主要有电饭（火）锅、电热水器、电热取暖器、白炽灯、加热器等。要进行分类计算。
　　有功计算负荷等于同类用电设备的容量总和乘以一个需要系数，即
　　Ｐｊｓ＝Ｋｘ?∑Ｐｅ
The purpose of load calculation is a reasonable choice to lead cross-section, to ensure that electrical wiring and equipment for economic and safe operation. Load calculation methods commonly used the "need factor" method, the method is relatively simple, high precision, and is a practical engineering method, which is widely used.
An electrical load calculation
Electrical equipment to determine the capacity of each will be followed by the electrical equipment classification, about pure resistive load and inductive load classification. Now houses mainly in the emotional load washing machines, air conditioners, refrigerators, electric fans, fluorescent in inductive ballast; purely resistive load of mainly electric rice (fire) pot, electric water heaters, electric heaters, incandescent , heater and so on. Calculated to be classified.
Active computational load is equal to the sum of the capacity of similar electrical equipment multiplied by a need to factor that
Pjs = Kx? ΣPe