Can someone please explain the difference between kW and kWh? Thank you!
Edit: thank you for all the responses, I appreciate you taking time to respond!
In: Physics
[deleted]
Disclaimer: I have no idea what I’m talking about.
Let’s say you have an appliance, that uses 1 kW of power. If you ran it for an hour, it would use 1kWh.
That is required because kW is a level of power, you aren’t buying 1 kW, you are buying the use of 1 kW for an entire hour. So 1 kWh is used there.
A kW is an amount of power, specifically 1000 Joules every second.
A kWh is a kilowatt, multiplied by an hour. 1000 J/s * 1h = 3 600 000 J
So a kWh is an amount of energy. Specifically it is the amount of energy used by a 1kW device every hour.
Think of a light bulb. A 100 Watt bulb wants to use 100 Watts of power when it is turned on.
Now, leave said light bulb on for 3 hours and you used 300 Wh (Watt-hours), which is literally calculated as [power] * [time]. The ‘kilo’ just moves the decimal point to handle larger numbers, so our example would be 0.300 kWh (kilowatt-hours).
Take 10 of those light bulbs and run them for 10 hours you get [100W] * [10h] = 1000 Wh
* [10 bulbs] = 10,000 Wh
/ [1000 kW conversion] = 10 kWh.
kW (kilowatts) is a measure of how fast electricity is flowing into something, like your house. kWh measures how much of that electricity has flowed into your house total.
Think about it like your water. You can run your taps at all sorts of speeds (in this case, your kW), but if you want to know how much water you’ve used, you also need to know how long you’ve run those taps for (your kWh).
You can work this out just by multiplying the water (or electricity) flow rate by the amount of time (hence why its kWh and not kW/h). This is because Watts is actually already a rate – of energy! Measured in Joules per second. So by taking some amount of kilowatts and multiplying is by how many seconds (or hours) you’ve used it for, you’re just calculating the energy you’ve used.
kW is power. kWh is energy.
Watts is a measure of a single point in time. A device or system is, at any given point in time, using a specific amount of power.
Energy is a measure over time. It’s how much power you’ve used over a specific period of time
kW measures power – it is the rate at which electrical energy can be delivered. kWh is a measure of work (or energy) – it is the amount of work that the power will do if applied for a specific period of time.
To use a water analogy:
kW is a rate and kWh is a quantity. kW would be analogous to gallons per second. kWh would be analogous to gallons. Different faucets in your house will expel water faster or slower. Your kitchen sink will expel 0.025 gallons per second while your shower might expel 0.1 gallons per second. If you let each of those run for a minute you’ll find that they will expel a different amount of water (shower more, faucet less).
In your daily life you’ll most likely encounter kW and kWh referring to electricity consumption. An appliance you own would be rated in kW (how quickly it will consume electricity) and you can use that to figure out how much electricity (and therefore how much $$$) it will use if you leave it on all day, half a day, for an hour, etc.
The difference between kW and kWh is the same as the difference between miles per hour and miles.
kW, or a kilo-Watt is a measurement of power usage, specifically it’s 1,000 Watts, or “joules per second”. A joule being the unit for work, or energy. So a Watt is basically the flow of energy required to perform a task, for example an 100W lightbulb requires 100 watts of power to produce light. A 1 kW generator is capable of powering (10) 100W light bulbs.
A kWh is a measurement of the rate that power is consumed (in other words, thousands of watts per second, per **hour**). For example, if I turn on (10) 100W light bulbs for one hour that would (1) kWh of power consumed. Electrical utilities will bill you according to the kWh of energy consumed.
Another way to look at it, a Honda Civic gasoline engine produces approximately 134kW of power for driving around. In this example, the kWh would be analogous to the amount of gasoline consumed as you drove around town.
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