功率因数PF等于有功功率（千瓦）除以视在功率（千伏安），公式为：‌PF = 有功功率（kW） ÷ 视在功率（kVA）。

打个比方，我们购买一杯啤酒，以杯子大小来支付费用。但是在杯子中有啤酒和啤酒沫，啤酒越多泡沫就越少，我们的花费就更划算。啤酒代表有功功率，是我们真正需要的有用的商品；泡沫代表无功功率，是没用的商品，我们不能使用它，所以不想要太多。它们合在一起就是视在功率，是我们的实际功率。所以说功率因数就是有用功率与实际功率的比值，或者说是啤酒和我们所支付杯子大小的比值。您理解了吗？

What is power factor?

Power factor (PF) is equal to the active power (kW) divided by the apparent power (kVA), expressed by the formula:
PF = Active Power (kW) ÷ Apparent Power (kVA).

For example, when we buy a beer, we pay the cost based on the size of the glass.

However, in the glass, there is both beer and foam. The more beer there is, the less foam there will be, making our spending more cost-effective.

The beer represents active power, which is the useful commodity we truly need; the foam represents reactive power, which is a useless commodity that we cannot utilize and therefore do not want too much of.

They together form the apparent power, which is the total power we actually handle. Therefore, the power factor is the ratio of useful power to the apparent power, or in other words, the ratio of beer to the size of the glass we pay for. Does this make sense?