容量因子（Capacity factor）是发电厂的平均发电量除以额定容量，介乎0到1。不同类型发电厂的容量因子会有很大差异。

一般而言，核电厂通常24小时以满载额定容量运行，容量因子接近1。停机维修时，容量因子便是0。

可再生能源的容量因子则会受天气影响。在夏季，水电厂平均发电量会较高，容量因子便较高。

如果发电厂以较高的容量因子运作，其发电平均成本会较低。因为可以摊薄固定成本，如投资发电机及租地的支出，令电力公司可以赚取更大利润。因此，一些电力公司会提供累退式的收费，用电量愈多，电费愈平宜，吸引工厂使用更多电力。

The net capacity factor of a power plant is the ratio of its actual output over a period of time, to its potential output if it were possible for it to operate at full nameplate capacity continuously over the same period of time. To calculate the capacity factor, take the total amount of energy the plant produced during a period of time and divide by the amount of energy the plant would have produced at full capacity. Capacity factors vary greatly depending on the type of fuel that is used and the design of the plant. The capacity factor should not be confused with the availability factor, capacity credit (firm capacity) or with efficiency.