很多人经常把“功率”和“能量”混为一谈。当你看到电费单上的 100 kWh（千瓦时），或者食物包装上的 500 kcal（大卡）时，你其实是在和能量打交道。而当你谈论空调的 2000W（瓦特）或跑车的 400 匹马力时，你谈论的是功率。它们之间究竟有什么联系？
Many people confuse "Power" with "Energy". When you see 100 kWh on your electric bill or 500 kcal on a food label, you are dealing with Energy. When you talk about a 2000W air conditioner or a 400hp sports car, you are talking about Power. What's the link between them?
能量 (Energy) 是做功的总量；功率 (Power) 是做功的速度。
Energy is the total work done; Power is the rate at which work is being done.
1. 瓦特与马力的战争 / Watts vs Horsepower
瓦特（W）是国际标准单位，为了纪念蒸汽机改良者詹姆斯·瓦特。而“马力（hp）”则是一个更古老的单位。最初，瓦特为了向矿主们推销蒸汽机，需要一种方式来形容机器能抵多少匹马。1 匹马力大约等于 746 瓦特。直到今天，尽管科学界统一使用瓦特，但汽车行业依然钟情于马力。
The Watt (W) is the international standard unit, named after James Watt. "Horsepower (hp)" is an older unit. To sell his steam engines, Watt needed a way to explain how many horses a machine could replace. 1 hp is roughly 746 Watts. Today, while science uses Watts, the auto industry still loves Horsepower.
2. 卡路里：身体的燃料单位 / Calories: The Body's Fuel
卡路里（Calorie）本质上也是一种能量单位。1 卡路里的定义是将 1 克水升高 1 摄氏度所需的能量。在物理实验中我们常用焦耳（Joule），但在营养学中，卡路里依然统治地位。1 大卡（kcal）等于 4184 焦耳。这意味着，一个 500 大卡的汉堡包含的能量足以让一个 100 瓦的灯泡点亮将近 6 个小时。
A Calorie is also a unit of energy. 1 calorie is defined as the energy needed to raise the temperature of 1 gram of water by 1°C. While physics uses Joules, nutrition sticks to Calories. 1 kcal = 4184 Joules. This means a 500 kcal burger has enough energy to power a 100W light bulb for nearly 6 hours.
结论 / Conclusion
Whether you're saving money on electricity or losing weight by counting calories, accurate unit conversion is the first step. Use our Energy Converter to calculate heat or our Power Converter to compare appliance efficiency.