Kilowatts and horsepower measure the power of different systems in various fields. The most common include electrical engineering, mechanical engineering, power generation, and the automobile industry. Whether you’re a part of these industries or not, it’s good to know the difference between “kilowatts vs horsepower” to apply them correctly.
The kilowatt (kW) is the unit of power an electrical appliance uses. It is generally used to calculate energy. On the other hand, horsepower (hp) defines the power consumption in mechanical devices, such as cars and boats. The rate is typically expressed in foot-pound-second (fps or ft-lb/s), but you can also convert it into watts.
Because both units measure power, are they different from each other? To understand them better, let’s explore common similarities and dissimilarities between these units.
Kilowatts vs Horsepower: Side-by-Side Comparison
| Kilowatts | Horsepower | |
| Inventor | James Watt | James Watt |
| Year of Invention | 1882 | 1700s |
| Use | measure the power of electrical systems | Measure the power of mechanical systems |
| Unit | SI (metric system) | Not a standard unit |
| Types | Only kilowatts | Brake horsepower, Metric horsepower, Electrical horsepower, Boiler horsepower, etc. |
| Conversion into Watts | 1 kW=1000 watts | 1 hp=745.7 watts (varies between 735.5 watts to 750 watts) |
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Kilowatts vs Horsepower: What’s the Difference?
Kilowatts and horsepower both measure the power different appliances use. However, you can’t use either to measure any device. This means both units measure power in varying systems—kilowatts for electrical and horsepower for mechanical.
Are there any other differences? Yes, there are. Let’s explore them in this kilowatts vs horsepower comparison to understand where to apply and how to calculate each power unit.
Kilowatts Explained
The watt (W) is the standard SI unit for power, and 1000 watts equal 1 kW. The unit is inspired by its inventor, a Scottish physicist James Watt in the 1700s. He contributed significantly to the energy units in the late 17th and 18th centuries.
To understand kW deeply, you must know what power is and how it relates to energy. The word “energy” comes from the Greek term “energeia,” meaning activity or operation. So, energy is the process that operates an action.
You can’t observe energy directly. Instead, measuring the external properties is essential since energy comes in various types. The three most common ones are thermal energy, kinetic energy, and potential energy. So, how does it relate to power? Power is actually the rate at which energy is produced or converted.
Power is calculated in joules per second or watt. One thousand watts combine to form a kilowatt. Multiplying the wattage of an appliance by time gives energy, which is measured in kilowatt-hours.
Kilowatts Applications
The kilowatt is mainly used to calculate the power or wattage of an electric appliance, such as a microwave, electric oven, PC, TV, and more. You may have seen kW mentioned on your electricity bill as “kilowatt-hour (kWh).” It represents the electricity you consume over a certain period.
The kilowatts also measure more significant power values in large appliances like cars. Using watts for this purpose is unsuitable. Instead, you will need to consider a higher power unit like kilowatts. In fact, the Southern Hemisphere uses kilowatts to express the power a vehicle generates.
However, horsepower is preferred to measure power produced by different vehicle components. We will discuss it in detail in the horsepower heading.
Kilowatts Calculation and Conversions
You can calculate the kilowatt from the standard formula for measuring power. It is:
P(W) = W / ∆t
Where,
P(W) = power in watts
W = work
∆t = elapsed time
Since one kilowatt has 1,000 watts, the formula for kilowatt becomes:
P (kW) = P(W) / 1,000
Suppose a microwave oven that consumes 500 watts every hour. You use it for an hour 10 days a month. How much power will the microwave oven use in kilowatts at the end of the month? Here is how you can calculate it:
Total power consumption for the month = 5,000 watts
Power (kW) = 5,000 / 1,000
Power (kW) = 5kW
You can convert kilowatts into other power units as well, including horsepower (hp), brake horsepower (bhp), and metric horsepower (PS). Every conversion will look like this:
- 1 kW = 1.34102 hp
- 1 kW = 1.34 bhp
- 1 kW = 1.35962 PS
Horsepower Explained
There is a tie in this “kilowatts vs horsepower” one-on-one regarding their creator. The same Scottish physicist James Watt invented horsepower (hp) in the 18th century to measure the power generated by draft horses and steamboats. This unit was found to describe the power output of a vehicle’s engine.
The horsepower is the work performed by a 550-pound (lb) force through a foot in a second. You can also call it foot-pounds of work. Many countries that don’t strictly use the SI system opt for horsepower to calculate power in electrical motors, vehicles, and similar mechanical appliances.
A horsepower’s value varies depending on its form. For example, one brake horsepower (bhp) equals 745.7 watts. It is the power of a vehicle’s engine, excluding its gearbox and other attached pieces of equipment. Similarly, one metric horsepower (PS) translates to 735.5 watts, and one electrical horsepower refers to 746 watts.
The hp’s value range starts from 735.5 watts to 750 watts. Other types of horsepower are boiler, CV, metric, etc. Contrary to the common misconception, horsepower isn’t actually the power of a horse.
Horsepower Applications
Horsepower measures the power output difference between vehicles’ engines and similar mechanical appliances. Hp is directly related to a car’s speed. The higher the hp, the faster the vehicle will move.
The hp varies depending on the size of the car. For example, a small vehicle will have 100 bhp of power, while a big troller will generate 500 bhp. You can also use horsepower to express how much work different mechanical machines do, such as pumps and generators. A small pump may produce one hp, and a large one may have 3000 hp.
Horsepower also expresses how much power an electric motor produces. A small engine will have one hp, while a large one can have 10 hp. You can also use this power unit to calculate the power output of electric vehicles (EVs).
Horsepower Calculation and Conversions
One significant difference between kilowatts vs horsepower is that the hp isn’t the SI power unit. That is why many people consider it a hypothetical measurement. It is also because hp doesn’t involve energy loss. The horsepower’s formula is as follows:
HP = (F x d) / t
Where,
F = force in pounds
d = distance in feet
t = time in minutes
Suppose your vehicle’s engine produces 300 pounds of force while moving at 2 feet of speed per second. Its horsepower will be:
HP = (300 x 2) / 1
HP = 600
You can also write the above equation as:
Horsepower = Torque x RPM / 5,252
You can convert horsepower into different power units, such as brake horsepower, metric horsepower, and watts. Here is what it will look like:
- 1 hp = 745.7 W (0.7457 kW)
- 1 bhp = 746 W (0.7462 kW)
- 1 PS = 735 W (0.7354 kW)
Kilowatts vs Horsepower: Which Do I Use?
Watt, kilowatt, and horsepower are units that measure power, each representing a particular rate of expenditure. They were all invented by James Watt during the 17th and 18th centuries. His goal was to quickly calculate the power output of different electrical and mechanical systems.
Watt measures small power output, and kilowatt calculates higher rates of energy an appliance generates. Both are generally used for electrical devices. On the other hand, horsepower indicates the power a mechanical device produces, mainly automobiles.
Watt is the SI power unit. Meanwhile, horsepower is typically a hypothetical power output a vehicle produces since it doesn’t account for lost energy.
One kW refers to 1,000 watts, but the value for horsepower varies depending on its form. The most commonly-used horsepower types are brake horsepower (bhp), metric horsepower (PS), and electrical horsepower. A bhp equals 746 watts, PS is 735 watts, and hp is 745.7 watts. The typical range stays between 735 to 750 watts.
So, always use horsepower to refer to the power output of vehicles and kilowatts for electrical appliances. That’s the correct way of using both of these power units.
