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Here’s what it’s all about: Power and work
Whether it’s a microwave oven or a refrigerator, almost all household appliances use the term "kW", i.e. kilowatt. But sometimes also from kilowatt-hour, abbreviated "kWh". What is the difference? The answer is: kilowatt describes a "power". Kilowatt hour, on the other hand, is a measure of the amount of "work".
Kilowatts – power – is about how much energy you use or generate in an instant, or in other words, "how fast" you use or generate energy. A kilowatt-hour, on the other hand – work – is equal to the energy consumed or generated at a given rate over a period of time. For example, when a 100-watt lamp burns for ten hours or a 5-megawatt wind turbine turns for a week.
It’s like in sports. "Power," or kW, tells you how fast a sprinter is – that is, "what he can do". If it runs at this top level for an hour, "kWh" represents its energy consumption during the entire sprint.
The "h" makes the difference
Time makes the difference. That’s what the "h" stands for. It is the abbreviation for the Latin word "hora", in German: "Stunde". In physics, however, kilowatt hours do not refer to "hours of power," but rather to "work.
Small "k", big "W": The "can what"
But let’s go back a step. One kilowatt is a thousand watts. Named after the Scottish inventor James Watt, who was born in the 18th century. lived in the twentieth century. Today, its name stands for converted energy worldwide. For example, it is electrical energy – i.e. electricity – that becomes light in the living room. Or about energy in fuels – such as oil – that comes as heat from the heater. The more of it is implemented in one moment, the more watts the lamp or the heater has – so the more it can "perform".
Megawatt show how much a wind turbine can do
The specified power also describes how much electricity, for example, a wind turbine can produce at a maximum in a moment. In the nineties, an onshore wind turbine had an average maximum generation capacity of about 600 kilowatts. Today wind turbines can do much more. In the meantime, there is talk of millions of watts, i.e. megawatts (MW). 7.5 MW is the capacity of a wind turbine on land today. A huge development.
Knowing is one thing, needing is another
What a system like a wind turbine or an energy-saving lamp "can do" is one thing. The other thing is how much energy actually flows. The light in the living room is off during the day, and the wind turbine doesn’t turn when the wind is not blowing. Which brings us back to "kWh" again.
So kilowatt hours are about the "consumption" or "generation" of energy – whether by lamps or wind turbines. Electricity consumption, for example, is shown in kWh on the electricity bill. An average 4-person household in Germany consumes approximately 4.200 kilowatt hours of electricity.
The thing with calories
By the way: There are also other terms for performance and work. One kilowatt, for example, is 1.36 horsepower. One kWh corresponds to 3.6 million joules or about 860 kilocalories. But: Who would count the kilowatt-hours to decrease?