KW stands for power, which is a physical quantity that describes the rate of energy conversion or transmission. All electrical equipment in our life require power units such as kW, kWh, and HP to perform normal woks.

What is KW?

KW(Kilowatt) is a commonly used unit of power, especially in the industrial and commercial fields. Taking the electricity market as an example, energy exchanges charge in kilowatt-hours (kWh), that is, the unit of electricity consumption is calculated based on kilowatts. Kilowatt is also a common unit of power for computer servers, engines, generators, air conditioners and many other equipment.

The use of kilowatt as a unit of power can also be traced back to 1889 when the International Electrotechnical Commission was established, which identified a new unit that could conveniently measure power. Power is everywhere in our lives, for example, our home appliances, cars, elevators, factories, etc. all require power to perform various tasks.

Electric power

What is power? Power is a physical quantity that indicates how fast an object does work. In physics, power(P) = work(W) / time(t), and the unit is watt (W). Common power units in our daily life include kW, PS, HP, BHP, WHP, and cV used in Italy before. Kilowatt is the international standard unit, 1kW to W = 1000 W.

Watt is a power unit in the International System of Units, which is defined as the energy converted or transmitted per second, and can also be understood as the energy consumed per second or the work done per second.

Kilowatt (kW) is one thousand times the watt, indicating that the energy consumed per second is one thousand times the watt. 1000 joules of work is done in 1 second, its power is 1kW.

Electric power indicates how fast the current does work, that is, how fast the electric energy is produced or consumed. The units we commonly use kW, MW, and GW are equal to one thousand watts, one million watts (equal to 1000 kilowatts, that is, megawatts), and one billion watts (equal to 1000 megawatts).

KW application

In a power plant, the kW of a generator indicates the rate at which it produces electrical energy, and the installed capacity is the sum of the rated active power of the generator sets actually installed in the system.

On the power consumption side, the kW of a household appliance refers to the rate at which it consumes electrical energy. For example, a 100W bulb has greater power and brightness than a 60W bulb, and consumes more electricity per unit time.

In the field of electric motors, the kW of a motor indicates the rate at which it converts electrical energy into mechanical energy.

The greater the power, the more electrical energy is converted per unit time, which means that the more mechanical energy it produces, and the greater the productivity of the machine driven by the motor.

What is kilowatt per hour?

Kilowatt per hour(kWh) is a unit of electricity, scientifically known as kilowatt-hour, which indicates the amount of electricity consumed by an appliance with a power of one kilowatt in one hour. kWh is also the symbol of the unit of electricity measurement

Electric energy is a statistical unit that indicates how much work is done by electric current. The international standard unit of energy is familiar to everyone, which is joule(J). For example, 60 joules is equivalent to the amount of electricity required to light a 60 watt light bulb for one second.

(what is kilowatt-hour？)

However, in the power system, it is usually expressed in kWh and MWh, 1MWh to kWh = 1000 kWh, 1 kilowatt-hour to joules = 1000 watts * 3600 seconds = 3600 kilo-joules = 3,600,000 joules. 1kWh is the amount of electricity produced or consumed by a device with a power of 1kW in 1 hour.

Connection and difference of kWh vs. kW:

Both units are used to express the process of producing and consuming electrical energy, but kW expresses the speed of the process, while kWh expresses the total flow of electrical energy in the process. Just like one can use meters per second to describe speed, but can only use meters to express distance. Both units can be used to describe a distance, but the emphasis is different.

KW vs. HP

What is HP (horsepower)?

In daily life, we also refer to power as horsepower, with the unit being HP, just like twisting force is called torque.

In a car, the largest work machine is the engine. The power of the engine is calculated by the torque, and the calculation formula is quite simple: Power (W) = 2Tx torque (Nm) x speed (rpm) / 60. After simplifying the calculation, it becomes: Power (kW) = torque (Nm) x speed (rpm) / 9549.

The imperial standard for horsepower (HP) is defined as: A horse pulling a 200-pound object 165 feet in one minute, which is multiplied to 33,000 lb-ft/min.

The metric horsepower (PS) is defined as: A horse pulling a 75kg object 60 meters in one minute, which after multiplication is equal to 4500kgm/min.

Convert kW to HP

However, how do we convert kW to HP that we are familiar with? Due to the difference between the imperial and metric systems, the conversion of kW to HP is also different.

After unit conversion, (1lb ≈ 0.454kg; 1ft ≈ 0.3048m), 1HP ≈ 4566kgm/min, which is slightly different from the metric 1ps ≈ 4500kgm/min. If converted in watts (1W = 1N.m/sec ≈ 9.8kgm/sec), 1HP ≈ 745.7 W; 1ps ≈ 735.5 W, two different results, a difference of about 1.5%.

1 kilowatt = 1,000 watts (Watt) = 1000 joules

1 kW to HP ≈ 1.341 HP (horsepower)

1 kW to PS ≈ 1.3596 PS (metric horsepower)

1 kW to N.m/s = 1,000 N.m/s (Newton meters/second)

1 kW to kcal/s = 0.239 kcal/s (kilo-calories/second)

Notes:

energy can take many forms, such as wave energy, magnetic energy, mechanical energy, etc. Regardless of the type of energy, it can be measured in several different units of energy.

The most common of which are joule and watt. Watt is mainly used to measure power consumption, while joule is the most commonly used unit in physics to accurately measure energy.

1 joule is the work done by a force of 1 Newton to move an object 1 meter.

1 newton is defined as the force that causes an object with a mass of 1 kg to produce an acceleration of 1 m/.

In summary, kilowatt (kW) is a unit of power based on watts, representing the energy consumed per second, and can describe the rate of energy conversion and transmission in the power system. Kilowatt is widely used in many fields such as power market, equipment manufacturing and energy management.

Understanding what does kW stand for and conversions of kW to HP and other units can better help you determine what size air compressor do I need.

KW to CFM

Basic concepts of air compressor power and air volume

Air compressor power refers to the energy consumed by the air compressor during operation, usually expressed as power consumed per unit time, in units of kW or HP. Air volume refers to the amount of air sucked in or discharged by the air compressor per unit time, usually in units of m³/h or CFM.

KW to CFM conversion

In practical applications, it is sometimes necessary to convert the power and air volume of the air compressor. And the gas flow rate will change when it’s under different conditions, therefore there are two flow rate units: SCFM vs CFM. Below are some common KW to CFM conversion formulas:

1. Under standard gas conditions, the conversion relationship between power and air volume is as follows:P = 1.2 × Q × ΔP × η / 1000Wherein, P is power (kW), Q is exhaust volume (m³/h), ΔP is pressure loss in the pipeline (mmAq), and η is air compressor efficiency.

2. At room temperature, different gases have different volume weights, so corrections need to be made when converting. Taking air as an example, the following formula can be used for conversion:P（kW）= Q（m³/h）× ΔP（Pa）÷ 3600÷ 1000 ÷ 1.23Among them, 1.23 is the volume weight of air, in kg/m³.

3. The air volume will also change under different densities. If you need to convert the air volume from the standard state (density is 1.2kg/m³) to other states, you can use the following formula:Q1 = Q2 × ρ2 ÷ ρ1Where Q1 is the air volume under the standard state, Q2 is the air volume before conversion, ρ1 is the standard gas density, and ρ2 is the gas density after conversion.

Another CFM to kW conversion formula can be less complex to understand: check the CFM rating in the air compressor nameplate that air compressor manufacturers installed. Then look up to the air compressor motor kW rating of its nameplate.

The simplified conversion formula of kW to CFM is: kW to CFM = air compressor CFM rating ÷ motor kW rating, then you will know how many CFM your air compressor can generate by 1 kW of electricity. And CFM to kW = air compressor motor kW rating ÷ CFM rating.

KW and other unit conversions

Conversions of air flow rate to volume

• 1 CFM to m3/hr ≈ 1.699 m³/hr ≈ 0.4719 l/s
• 1 m³/hr ≈ 0.5886 CFM
• 1 l/s ≈ 2.119 CFM
• 1 FPM ≈ 0.3048 m3/min ≈ 0.00508 m/s

KW to cooling capacity conversions

• 1 kW to kcal ≈ 860Kcal (kilocalories)
• 1 Btu (British thermal unit) ≈ 0.252kcal ≈ 1055J
• 1 Btu/h ≈ 0.252kcal/h
• 1 Btu/h to Watt ≈ 0.2931W
• 1kW ≈ 0.2843 RT (cooling capacity) ≈ 860 kcal/h ≈ 3.412 ×10⁻³MBtu/h

Pressure units conversions

1 Bar in PSI ≈ 14.5 PSI ≈ 0.9869 atm ≈ 0.1 MPa ≈ 100 kPa ≈ 1.01972 kgf/cm2

1 kg/cm 2 ≈ 9.8 × 10⁻⁴Pa (Approximately 10⁻⁵Pa) ≈ 10 mmH₂O ≈ 0.98 Bar = 0.098 MPa

1 Pa ≈ 0.102 mmH₂O ≈ 1.02 ×10⁻³ mmH₂O

1 mmH₂O ≈ 9.8 × 10⁻³ kPa = 9.8 kPa

HP to Ampere and kW to Ampere

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