Differences between Power vs. Energy: [kW vs. kWh]⚡2025
Posted 6 Jun
Posted 6 Jun
Today, with so much interest in electricity, whether it be via home solar
systems
or more recently, electric vehicles (EV's), the confusion between power and energy
and how they are related.
Power is that force which moves vehicles, heats our water, powers
our electronic devices and so on.
Power = kW (Kilowatt)
Energy is the amount of power being used over
time.
Energy = kWh (Kilowatt-hour)
Power, which is measured in Watts (W), Kilowatts (kW), and Megawatts (MW), represents how quickly work can be done and how fast energy can be produced or consumed.
Say if you had a car at a stop-still, and needed to accelerate to 60 km as fast as possible, the car would accelerate and use lots of power to propel the vehicle forward to reach 60 km within 20 seconds.
Energy on the other hand, is different because it measures how long that vehicle needed to produce power. The energy needed is greater when the time is reduced to match the power output, whereas if the vehicle had more time like 40 seconds, the power usage wouldn't be as much, therefore reducing the overall energy needed.
Energy is also measured in the same way power is, however has a time aspect added. Watt-hours, Kilowatt-hours, and Megawatt-hours.
Have you heard the term kW?
Watts (W), Kilowatts (kW), and Megawatts (MW) are all units of measurement of power. So you'll notice when
looking at EV chargers, they'll mention '7kW of charging' etc.. This is what it is referring to.
An example differentiating Power and Energy is electric vehicles. Electrical power from the battery produces that force which propels the vehicle forward.
Energy is the result of that power being used over a certain amount of time. Electrical power multiplied by the time is the energy.
How about Electric Vehicle charging?
As mentioned before, EV chargers are generally measured in kW's which indicates the speed that it recharges at.
We install a 360kW charger, which can provide the full 360kW of DC power into the 81 kWh battery in the Tesla Model Y.
In a perfect world with no losses etc. the Tesla would fully-charge in just over 14 minutes.
81 (kWh) ÷ 360 (kWh) = 0.225 which put into
minutes is 13.5 minutes.
Solar panels are measured in watts (415W solar panels) and when in an array, that system ranges anywhere in the kilowatts (a 6.6kW solar system). This total generation capacity is calculated by simply adding the entire systems' production potential if the sun is completely visible etc.
An inverter also works in kilowatts as it is in charge of converting DC power from the solar panels to AC power which the house can use.
Battery storage however, is typically measured in the amount of energy (kWh) which indicates the maximum storage capacity. If a home battery had 15 kWh of Energy, with a maximum output of 5 kW of Power, the battery would be able to last 3 hours at that maximum power output.
Most product datasheets have information indicating what the product ratings are with kW's and kWh's.
Hopefully you have a better idea on the differences between Power and Energy!
If you'd like more information on electrical topics like this, please feel free to have a look around at our other articles which cover topics like AC vs. DC, Single vs Three Phase etc.
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