The key difference between kW (kilowatts) and kVA (kilovolt-amperes) lies in the fact that kW is a measure of real power, while kVA is a measure of apparent power. Here’s a breakdown of the differences:

1. Power Type

• kW (Kilowatt): Represents real power or active power, which is the actual power that does work in a system. It’s the power that is consumed by electrical equipment to produce useful work, like running a motor, lighting, or heating.
• kVA (Kilovolt-ampere): Represents apparent power, which is the total power flowing in the system. This includes both real power (kW) and reactive power (the non-working power caused by the magnetizing current needed to maintain magnetic fields in inductive devices like motors and transformers).

2. Power Factor (PF)

• The relationship between kW and kVA is determined by the power factor (PF), which measures how efficiently the current is being converted into useful work.
• Power Factor (PF) is a number between 0 and 1, and it is defined as:

Power Factor (PF)=kW / kVA

• kW = kVA × PF
• A power factor of 1 (or 100%) means all the power is being used effectively as real power, and in this case, kW = kVA. If the power factor is less than 1, some of the power is wasted as reactive power, and kW will be less than kVA.

3. Application

• kW (Real Power): Used for rating devices that consume electricity and perform actual work, such as heating elements, light bulbs, or motors. Power bills are usually based on kW consumption.
• kVA (Apparent Power): Used for sizing electrical systems like generators, transformers, and UPS systems, because these systems must handle both the real and reactive power. kVA represents the total load on the system.

4. Formulas for Calculation

• kW (Real Power): kW=Voltage (V)×Current (I)×Power Factor (PF)
• kVA (Apparent Power): kVA=Voltage (V)×Current (I)÷1000.
• The power factor is not included in the calculation of kVA, which is why it is called apparent power.

5. Utility and Billing

• kW is the useful power that actually performs the work, and utility companies often charge customers based on the kW usage.
• kVA is important when sizing electrical equipment like generators, since generators need to supply the total apparent power (both real and reactive).

Example:

• If a generator is rated at 100 kVA and has a power factor of 0.8, the real power it can supply is: kW=100×0.8=80 kW

This means the generator can supply 100 kVA of apparent power, but only 80 kW of that is doing useful work, while the rest is reactive power.

In Summary:

• kW (kilowatts) is the actual power that performs useful work.
• kVA (kilovolt-amperes) is the total power (including both real power and reactive power).
• The difference between them depends on the power factor, which measures the efficiency of power use in the system.