Why are Electric Car Batteries Measured in Kilowatt-hours (kWH) and Not Ampere-hours (Ah)?-A Complete guide 2024

Why are Electric car batteries measured in kilowatt-hours (kWh)?

If you’ve ever carefully examined your power account, you probably noticed that your service provider counts the number of kilowatt-hours of energy you use (kWh). Why are Electric Car Batteries Measured in Kilowatt-hours (kWh)?

Electric car batteries measured in kilowatt-hours(kWh) because simply knowing the amp-hours, not itself, indicate the battery’s capability. Kilowatt-hours are best rated for very large batteries (a kilowatt-hour is 1,000 watt-hours)and thus electric car batteries measured in kilowatt-hours(kWh)

Most people want a convenient number to refer to capacity, and this value is only helpful if you know the voltage.

You can calculate the battery’s capacity by utilizing watts-hours rather than amp-hours because watts equal volts times amps. Let’s see in detail the description.


Kilowatt-Hour Batteries are used in Electric Vehicles (kWh)

Running electric car

Kilowatt-hours are best rated for very large batteries (a kilowatt-hour is 1,000 watt-hours)and thus electric car batteries measured in kilowatt-hours(kWh)

Kilowatt-hours are a far more practical unit of measurement to use when comparing different cars because most people don’t know or care about the current voltage or the exact current.

Instead, they want to know how far a charge can last.

Additionally, if you are aware of the battery’s watt-hour capacity, you can divide watts by tension to obtain amp-hours (or kilowatt-hours).

For instance, the battery in my Nissan Leaf is 24 kWh. About 360 volts are required to run the system. The capacity is therefore roughly 66 amp-hours at such voltage.

You could say that the car battery can hold 66 amp-hours at 360 volts, but it’s much easier to say 24 kilowatt-hours.

People frequently believe that a charger’s kilowatt rating determines how quickly it can charge a battery, but this is untrue.

Even a charger with a high output takes longer to charge the battery’s final 20% of capacity because it is more difficult to cram energy into the cells at such a rapid rate.

This is the reason why battery makers and manufacturers of electric vehicles that use these batteries talk about charging from 0% to 80% using their DC chargers in their presentations.

When using these DC chargers at the charging stations, many drivers would rather leave when the battery is 80% charged than wait for the final 20% to catch up.

What does KWh mean for an Electric Car?

Almost every evaluation of an electric vehicle will use the term “kWh,” but what does it mean? Getting to grips with all the terminology associated with electric cars might be one of the most difficult aspects of switching from gasoline to electricity for many consumers.

Where you might be used to all the regular car-related terminology, terminology like ‘kilowatt-hours’ (kWh) which is used when talking about electric automobiles, may be less familiar.

When looking for a new electric car, it’s crucial to comprehend quantities like kWh and even Ah and what they mean because they explain things like charging times, battery capacities, range, and efficiency.

What does kWh mean for an Electric Car?
What does kWh mean for an Electric Car?

A Note on Amperes (A) 

Electric current is measured over time using an ampere, also known as an amp.

A running water tap is an analogy for an electrical circuit. Two things are necessary to force water out of a faucet: water and pressure.


When you push water through a pipe from one end, it also travels forward at the other end, just like electrons do in a line, in the same way, that electrons flow through a circuit similar to how water flows through a faucet.

Voltage is referred to as the “electrical pressure” that is employed to move these electrons.

The amount of electrons (water) that flow past a certain location in the circuit (the tap’s end) in one second is measured in amps.

The usual definition of one ampere (A) is 6.24 x 10 to the power of 18 electrons flowing in a second. The current increases as the amps increase.

A note on Ampere-Hour (Ah)

A different measurement than amps is an amp hour (Ah), which is used to calculate how much water, or energy, can fit in a bucket or be stored in a battery.

Simply put, it refers to how much current a battery can produce in an hour. Therefore, amp hours are utilized to calculate battery life.

The battery life in hours is calculated by dividing amp hours by amps.

A 2Ah battery can therefore draw two amps for an hour or four amps for 30 minutes before it runs out.

Kilowatts and Kilowatt-Hours

A watt is a measure of power that is determined by dividing the amount of electrical current (amps) by the force of the current (volts).

Let’s use the example of water to illustrate what would happen if two different types of hoses were used to spin a water wheel.

The water wheel is spun by the total amount of electricity (wattage) applied to it despite only having one small hose and a low total amount of water (electrons) flowing per second (low current).

What Is the Significance of Kilowatt-Hours (kWh) in Electricity Measurement?

In reality, Kilowatt-Hours is a unit of measurement used by almost all home appliances, gadgets, and devices. However, what are Kilowatt-Hours (kWh) specifically and why do we use them so frequently?

It is measured in any watt-derived unit, not simply kilowatt-hours. Watt-hours (Wh) or megawatt-hours (MWh) could be used (MWh).

The reason why kWh is used as the unit of measurement for electricity is that it is simple to convert between different types of electricity use.

If you need to calculate tiny amounts of energy usage, you can use watt-hours; if you need to calculate big amounts, you can use megawatt (one kilowatt x 1,000) hours.

Also, the larger electrical grid uses this measurement to determine how much energy each household consumes;

As a result, electricity consumption is calculated in this way for all appliances and bills. Why? Because it’s just the greatest approach to uniformly measure the energy each of us consumes.

How Do You Calculate a Kilowatt-Hour?

Going with the unit of Kilowatt-Hour you must need to know how to calculate Kilowatt-Hour.

As stated previously, one kWh is equal to one kilowatt-hour (kWh) of energy used. Therefore, if a one-kilowatt item was running for an hour, you would use one kWh.

Two hours of operation would result in the consumption of two kWh, and so on. To calculate Kwh, you must be familiar with watts and time.

Here are a few examples.

1000w x 1Hr1kWh 
1W x 1000Hr 1kWh 
1W x 1Hr1Whr or since 1kWh1/1000kWh .001Kwh
20w x 3Hr60Wh/1000kWh.06kWh
400w x 24Hr9600Wh/1000kWh 9.6kWh
calculation in kwh

What does a Kilowatt Hour indicate?

We first need to understand watts to grasp this. You can determine a device’s energy usage by looking at its wattage.

kwh icon

Watt is nothing but a unit of power which in turn we use in electric cars. In reality, by dividing the volts by the amps, you may calculate the device’s wattage. You can therefore see how much power is flowing to your gadget at a given time.

In contrast, one watt multiplied by 1,000 is equal to a kilowatt. A kilowatt is merely a better-suited unit for larger measures, much like kilograms and kilometers are.

In essence, it informs us of the total energy consumed over time. For instance, a kWh is equivalent to 1800 watts of electricity used in an hour.

As a result, different devices will gradually use varying amounts of energy.

One kWh, for instance, may be consumed by a light bulb over 10 hours, whereas a microwave may do it in less than 15 minutes.

kWh can be used to determine how much energy has been produced. One kilowatt-hour (kWh) of energy, for instance, is produced by a solar panel system generating 1000 watts an hour.

Solar Charger Summary
Battery watts0W
Charge stateOff
Yield today1.16 kWh
Yield yesterday1.24 kWh
Solar Charger Summary


Electric Car Motor Power

The maximum output of the electric motor is what is meant by the term “power” in an electric car.

The power output of this is expressed in kilowatts (or 1000 watts), exactly like a conventional internal combustion engine (ICE).

More power is available at the expense of increased energy consumption with a higher kW value.

The table demonstrates how little difference there is between electric car power ratings and those of similarly sized and capable ICE cars.

Electric CarPower Ratings
Nissan Leaf 110kW
Hyundai Kona Electric 150kW
Mercedes-Benz EQC 300kW
Porsche Taycan Turbo S560kW
Tesla Model S Performance595kW
Electric Car and their Motor Power


Electric Car Battery Capacity

In kilowatt-hours, the total battery capacity of an electric vehicle is expressed (kWh or kW-h). You can find out from this rating how much electricity the battery pack can hold.

Similar to calories, it is an energy measurement unit, and one kWh is equivalent to 3600 kilojoules (or 3.6 megajoules). It is not a power unit like kW.

Smaller capacities are needed for electric cars with lower power output;

Electric CarBattery Capacity
Nissan Leaf40kWh
Hyundai Kona Electric64kWh
Porsche Taycan Turbo S93.4 kWh
Electric Car Battery Capacity

The Porsche would have the greatest range due to its greater battery capacity if all of these vehicles had the same electric motor (and thus the same maximum amount of electricity extracted from the battery at any given moment).

The Porsche, on the other hand, has a 560kW motor that is built for extreme performance at the expense of its 256-mile range.

However, while having a lesser battery capacity, the Hyundai Kona Electric has a 300-mile range because of its weaker motor.

Some people find the unit’s mention of “hours” confusing, but it’s quite straightforward.

The amount of energy needed to generate one kilowatt of power continuously for one hour is used to determine the kilowatt unit.

Kilowatt-Hours for your Electric Car

For every 100 kilometers driven, an electric car requires about 30 kWh. According to Edmunds, it’s simple to figure out how many kilowatt hours your automobile uses.

You will be charged $7.20 for a full charge of your electric car if it takes 40 kWh to fully recharge and the current rate is $0.18/kWh.

You will be charged $6 if your electric vehicle uses 30 kWh and the market price is $0.20 per kWh.

Although it fluctuates greatly depending on location, the price of energy is extremely steady. According to Edmunds, the average residential price varies from $0.9 in Louisiana to $0.28 in Hawaii.

The average is a little above $0.13. It is around $0.20 in California, where energy costs are often a little higher.

Using the information provided by the U.S. Energy Information Administration, you can determine the going rate in your region.

This chart displays pricing for the residential, commercial, industrial, and transportation sectors for the last two years across the United States.

Determine the Cost of your Electric Car’s Electricity.

There are numerous tools available to assist in calculating the cost of charging your electric vehicle.

There is a helpful car cost calculator available from the U.S. Department of Energy.

For instance, the fuel efficiency for a 2020 Volkswagen e-Golf automatic EV is 28/32 kWh/100 miles.

You can calculate your distances by driving 40 miles per day, five days per week, for 49 weeks of the year, with 45% of those miles being on a highway.

You travel 13,396 miles (6,109 on city streets and 7,287 on highways) annually.

If you live in Florida and log an additional 3,596 miles annually, your electricity use comes to 4,049 kWh. You spend $469 yearly on power or $0.20 per mile.

Your annual energy use in New York remains constant (4,049 kWh), but your power costs increase to $743 at a cost of $0.22 per mile.

Try calculating the cost using your electric car and state to see the results. If you want to purchase a new car, you can also do this in advance.

How Many Amps (Amp Hours) is a Car Battery?

Car battery

An electric car battery is measured in terms of Amp Hours but how much energy it stores? Is the energy in small car batteries is same as the large electric cars ? or there is a huge difference between them? Such questions are arising.

There are about 40 amp-hours in small car batteries. Around 50 amp-hours are the size of mid-sized batteries for larger automobiles and SUVs.

Batteries for bigger vehicles, such as trucks, can have a capacity of about 75 amp-hours.

Electric Car Battery Capacitor SizeAmp Hours Battery
Small40 amp-hours
Mid-sized50 amp-hours
Big75 amp-hours
Electric Car Battery Capacitor Size and Amp Hours Battery

As opposed to a deep cycle battery used to power electronics or appliances, automotive batteries are typically rated in CA or CCA (Cranking Amps, or Cold Cranking Amps).

Your 40-pound car battery is typically rated in cold cranking amps rather than amp-hours. Although it contains a lot of energy, it works best when it delivers that energy in brief bursts of high amps.

How many amps (amp hours) a car battery has to produce power depends on your situation and whether you have access to a marine or deep-cycle battery.

For converting amp hours to cranking amps or cold cranking amps, there is no set formula (or vice versa).

It would be similar to attempting to evaluate the efficiency of two vehicles by comparing their respective times from 0 to 60 mph and their respective average miles per gallon.

Although you might be able to find a few connections, correlations do not imply causality.

That didn’t stop us from conducting some studies to see if we could arrive at a generally agreeable rough estimate of the relationship between the two for a car battery.

How to Find Amp Hours of a Car Battery?

It is best to be cautious if you intend to deep cycle your car’s starting battery, which is something you shouldn’t do in any case if you value the battery’s life. Hence need to find the Amp Hours of an electric car battery.

In all probability, you won’t ever know the actual worth of the electric car battery if it doesn’t already have the amp hours listed on the label. You can only make educated guesses.

How to Find Amp Hours of a Car Battery?
How to Find Amp Hours of an Electric Car Battery?

In contrast to Europe, the USA rarely sees car batteries with the AH written on the tag.

You might be able to find your car in Europe and the replacement batteries for it online if you’re truly curious to get a better idea.

Approximate Car Battery Amps = Cold Cranking Amps x 0.11

Once more, there is no connection between AH and CCA. I did the best I could use data from a real battery charger manufacturer, but they are only estimations.

Justification for Cold Cranking Amp Ratings for Car Batteries

Car starter batteries are designed specifically for starting your car’s electronics and motor with a brief burst of amps rather than “deep cycling.”

The amount of amps produced for 30 seconds until the battery voltage drops to 7.2 at 32 or 0 degrees Fahrenheit, respectively, are measured in Cranking Amps or Cold Cranking Amps instead.

In essence, Cold Cranking Amps (or Cranking Amps) are the maximum amount of electricity your car can produce in a brief period to turn on the engine and power all of its electronic components, especially in cold weather.


Here we go through the main reason why we use to measure electric car batteries in terms of kilowatt-hours (kWh). We saw the significance of using kilowatt-hours (kWh).

We also go through the determination of the cost of our electric car electricity.

We hope that all of your questions about kilowatts (kW), kilowatt-hours (kWh), and ampere-hours (Ah) have been answered by this point.

Having a basic understanding of these concepts will make choosing an electric car easier than it was previously, and you will be able to select the vehicle you believe has the best battery.

Frequently Asked Questions.

What amps should I use to charge my car battery?

Almost all sizes and types of automotive batteries may be charged effectively using a 4-6 amp smart charger in float or maintenance mode.
By doing this, you can guarantee that your battery will receive a thorough and gentle charge that won’t damage it internally and will still fully charge it by morning.

How many Amps are needed to charge a car battery?

The pressure behind the amps, 13.8 volts, will cause your automobile battery, which is 12 volts, to start charging.
The owner chooses how many amps are used, although typical amp chargers are 1.5 or 2 amps for topping up or maintenance, or 4-6 amps to charge a battery from dead overnight.
Using a charger with 10 amps or more on a car battery is not advised.

Can Cold Cranking Amps (CCA) be converted to Amp Hours (AH)?

The CCA number can be multiplied by 0.1 or 0.11 to obtain a realistic approximation of a car’s amp-hours.
This should only be used as a rough estimate and not for applications that are crucial because your battery might be higher or lower.
Converting between CCA and AH is not achievable without testing each battery separately because there is no direct conversion between the two.

What is kWh in an electric car?

The amount of energy required to move a car is measured in kWh.
A-h only represents current capacity and does not represent energy until the voltage is taken into account. When comparing batteries of the same voltage and type, Ah is typically used.

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Bharat Suthar

I am principal creator of electriccarexperience.com. I like riding Electric Car, UTV in mountains and Terrain, Also I try to share all the real life experience here in the site.I am really dedicated to write about my experience. I love doing all the outdoor activity including riding electric car, dirt biking and hiking.

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