Are Kilowatts the New Horsepower?

What’s the difference between Kilowatts kW and Kilowatt Hours kWh?

Introduction

“I can’t believe the power of a cars engine used to be measured in number of horses” - this is what people in the future will say.

The term Horsepower was invented by a gentleman in the 1770’s. The horsepower unit was a marketing gimmick created to sell the newly invented steam engine. This gentleman understood that his potential clients would need a reference point to determine speed. He knew that many of his customers would use the machine to replace horses, so he set out to measure the power delivered by a horse.

This gentleman’s name was James Watt and ironically, his last name is exactly what will be replacing his once popular term - the kilowatt.

Overview: Kilowatts (kW) VS. Kilowatt-Hours (kWh)

I always like to use analogies to help explain concepts like these. Picture a fire hose filling up a swimming pool. The water flowing through the hose represents kilowatts, while the swimming pool represents kilowatt-hours.

Fire Hose (kW)

Kilowatts measure the rate of power. In respect to our analogy, kilowatts represent the speed at which the water travels through the hose. The larger the hose, the more water flows through it, and the faster it comes out the other end. In terms of EV Charging, kilowatts represent the electrical current flowing from the EV charger into the car.

Swimming Pool (kWh)

Kilowatt-hours represent the amount of energy stored. In respect to our analogy, kilowatt-hours is the swimming pool. It's the total amount of water (energy) stored in the pool (battery). For EV Charging, this is the size of the battery’s capacity. Kilowatt-hours indicate the energy stored in the battery, which can be used later to power the car.

What are Kilowatts (kW)?

Technically speaking a kilowatt is a unit of measurement for the rate of power an electrical device uses. Remember, a kilowatt is 1000 watts. As a reference point, an iPhone charger needs a minimum output of 20 watts to power an iPhone. In terms of electric vehicles, kilowatts (kW) represent the current of electricity flowing from the EV charger into the car, while kWh indicates the capacity of battery storing that energy.

What is a Kilowatt-Hour (kWh)?

Kilowatt-hour measures the consumption of electricity. In relation to electric vehicles, it represents the storage of energy in the battery. Remember, the concept of time is also embedded in kWh. For example, a standard microwave uses 1 kW of power to operate. If it runs for one hour, it consumes 1 kWh of energy. Evesco provides a great example in their article here.

Kilowatts to Horsepower Conversion

Now that we understand the concept, let’s talk about the fun stuff. Everyone knows that electric vehicles are fast. Very fast. This is mainly because electric motors generate instant torque, which is something internal combustion engines cannot do. The fastest electric car is faster than the fastest gas car but how do we compare them? Is there a way to convert kW to Horsepower?

Yes there is. Kilowatts are the new version of horsepower:

• 1 Kilowatt (kW) = 1.34 Horsepower (HP). For example, if you had an electric vehicle that was 208 kW like the Tesla Model 3 then that would be equivalent to 278 horsepower.

• Alternatively, 1 Horsepower (HP) = 0.75 Kilowatts (kW) so if you took a BMW 330i for example which has a horsepower of 248 that would be equivalent to 186 kilowatts.

Battery Pack is the New Gas Tank

In the past, a larger gas tank meant the vehicle could travel a longer distance. In terms of EV’s, a bigger battery pack means the same thing - it extends the cars range. That being said, some EV’s are more efficient than others. For instance, a 57.5 kWh battery in a Tesla Model 3 allows it to travel farther than a Ford Lightning pick-up truck using the same battery, due to the truck's larger size and weight.

I often use the Tesla Model 3 as an example because it’s the most common electric vehicle you’ll find on the road. The Model 3 has a 57.5 kWh battery pack and this battery enables the car to reach a range of 438 KM. This equals 7.6 kilometers per kW used.

On the other hand, the Ford F150 Lightning is a heavier, less efficient truck. It has a 131 kWh battery pack and a range of 515 KM, which equates to 3.9 kilometerrs per kW used. Just like gas cars, the heavier the vehicle the more juice it will require to keep moving.

Peak Charging Rate

The lower kW’s the battery can absorb, the longer the car takes to charge. A key to purchasing the right electric vehicle is charging speed. Some EVs charge up to three times faster than others, so unless you want to be waiting for your car to power up it would be wise to find an EV with fast charging capabilities.

For example, a Nissan Leaf hatchback has a peak charging rate of 100 kW. DC Fast Chargers usually offer a range of kW plugs, with outputs ranging from 50 kW to 350 kW. Basically, they provide different connections with varying speeds.

This means if you're traveling on a highway and spot a DC Fast Charger, you'll likely pull over to charge. Upon arrival, you might see plugs offering 100 kW and 350 kW. There will be no point to plugging your Leaf into the 350 kW charger, because it can only accept 100 kW of energy at a time. This would be a frustrating moment so choosing a car with the fastest charging is a must.

Conclusion

Kilowatts and kilowatt-hours are the new horsepower and gas tanks. Soon these terms will be common knowledge as more EV’s hit the streets. Measuring by horses will be a thing of the past as the majority of cars will soon to be powered by electricity. Electric vehicles bring many exciting features, including faster speeds, lower maintenance and cheaper power. I'm excited for this transition and hope this article sparks a bit of excitement in you as well.

As always, if you have questions or comments feel free to reach out. I’m here if anything comes to mind.

Catch you on the next one.

Arrivederci,

Strong Energy