Are you considering the rental of a generator for your business? During your research, you may have encountered the term ‘kVA’. While not commonly used outside of the industry, kVA is a unit that similarly expresses power to kilowatts (kW). In the following section, we will emphasise the critical distinctions between kVA and kW and provide instructions on converting between the two units.

The difference between kVA and kW is that one is a measure of power, and the other is a measure of energy. The most common use of these two terms is in the power industry, where they describe how much power a generator can produce.

Power Defined

Power is defined as the rate at which energy is used, expressed in watts. This can be calculated by multiplying voltage (V) by current (A).

Energy is the amount of work done by an electric current, expressed in joules (J). This can be calculated by multiplying voltage by current squared (V2 A).


kVA = kW x 0.836

Formula: kVA = kW x 0.836

Example:  If a load has 3 phase, 4 wire, 240 VAC supply with a current of 5 A, then its power rating would be 240 V x 5 A = 1200 W or 1.2 kW (1 kW = 1000 W). If this load was connected to a generator rated at 2 kVA, then to calculate its power output we would use the formula P = U x I and substitute into it 2 kVA for P: P = U x I = 2 kV x 5 A = 10 VA which means that it can produce 1.2 kW (1 kW = 1000 W).

What’s the Difference?

The main difference between kVA and kW in the context of generators is how they represent power.

kVA, or kilovolt-ampere, is a unit used to measure apparent power. It considers both the magnitude and phase angle of the electrical current and voltage in an AC (alternating current) circuit. Apparent power represents the total power consumed by a device or system, including valuable or accurate and reactive power.

kW, or kilowatt, on the other hand, is a unit that measures real power. Real power performs valuable work, such as running electrical equipment or devices. It does not consider any reactive power.
In simpler terms, kVA represents the total power capacity of a generator, including both the power used by devices and any additional power required for reactive components like motors or transformers. kW, however, reflects the actual power output or the energy the generator can deliver to perform useful work.

While kVA indicates the total capacity of a generator, kW represents the actual usable power output available for running electrical devices or equipment.

What is kVA?

kVA, or kilovolt-amps, is a measure of the power rating of a generator, motor or other devices. It is expressed as kilovolt-amps and is equal to 1,000 volts times amps. The abbreviation kVA is often used in place of kilovolt-amps.

kVA power ratings are important when choosing generators or motors for use in industrial settings. For example, if you need a motor that can help operate a conveyor belt in your factory, you will want to ensure that the motor has enough power so it does not overheat and stop working.

You can also use kVA ratings to determine if an electrical system has enough capacity to meet your needs. For example, if your business has several high-powered machines that need electricity to run efficiently, you might need more than one circuit breaker panel for each machine.

kVA Power Rating

The kVA power rating is a measure of how much current a generator can supply to a circuit. The higher the kVA power rating, the larger the capacity of the generator. The term “Kilovolt-Ampere” (kVA) is used to describe this measurement. The lowercase letter “k” stands for kilo, which means thousand. So, if you want to know how many watts your generator can produce at any given time, multiply its kVA by 1000. For example, A 5kVA generator will produce 5,000 watts of power.

You can calculate your kilovolt-amperes using this simple equation:

kVAR = Volts x Amps x Power Factor / 1,000

For example: If you have a 120V/240V system that draws 25 amps from each phase and has a PF of 0.8 (default), your total KVAR would be: 25A x 240A x 0.8 / 1,000 = 25kVAR or 30 kW

Rating the Amount of Power

The kVA (kilovolt-ampere) rating measures the amount of power that can be generated by a generator over time. It is calculated by multiplying the voltage by the amperage and then dividing that figure by 1,000. For example, if we have an output voltage of 240 volts and an input current of 12 amps, then our kVA rating would be 2,400 watts (240 × 12 = 2,880). This means that our generator can produce 2.8 kilowatts at any given moment in time.

A typical household circuit has 15-20 amps available for use at any given time and many appliances will not draw more than this limit; however, if you are installing several large appliances like air conditioners or electric clothes dryers on one circuit at the same time, then you may need to upgrade your electrical service by adding more circuits or upgrading existing ones with higher capacity breakers (which usually require professional installation).

kW vs kVA – Which One is Best?

Kilowatts (kW) and kilovolt-amperes (kVA) are both measures of power. The difference between kW and kVA is that kW is a measure of power over time while kVA is a measure of instantaneous power. The values for kW and kVA are calculated using different formulas, but they’re both used to determine how much energy appliances will use.

The formula for calculating kW is Watts = Volts * Amps, while the formula for calculating kVA is Volts * Amps / 1000. To calculate the amount of kW or kVA required to run an appliance, plug in its voltage and current draw into either formula, depending on whether you need to determine instantaneous or continuous power.

Understanding the Difference

In conclusion, understanding the difference between kVA and kW is crucial when choosing and utilising generators effectively. While kVA represents the total apparent power capacity, considering both real and reactive power, kW focuses solely on the actual usable power output.

By comprehending these distinctions, businesses can make informed decisions when hiring generators for their specific power requirements. Whether powering equipment, running appliances, or maintaining critical operations, Bellwood Rewinds, a reputable UK company, offers expert guidance and reliable generator solutions tailored to diverse business needs.

With this knowledge, businesses can ensure efficient and effective operation power management, promoting uninterrupted productivity and success.


kVA ratings help determine a generator’s total capacity and sizing requirements, considering both real and reactive power. kW ratings, however, indicate the actual power output available for running electrical devices. Both ratings are essential for selecting the right generator to meet specific power demands.

Yes, in some instances, the kVA and kW values can be equal. This occurs when the electrical load is purely resistive, without any reactive components. In such situations, the power factor is 1.0, aligning the kVA and kW values.

To convert kVA to kW, multiply the kVA value by the power factor (PF). The power factor represents the ratio of real power (kW) to apparent capacity (kVA) in an electrical system. The formula to convert kVA to kW is kW = kVA × PF.

Several factors can influence a generator’s power factor and efficiency, including the types of loads connected to the generator (resistive, inductive, or capacitive), the balance of the load, and the quality of the generator’s voltage regulation. Proper load management and power factor correction techniques can help improve power factor and efficiency.
Are kVA and kW ratings important for residential applications as well?

While residential applications typically have simpler electrical systems than industrial or commercial settings, understanding kVA and kW ratings can still benefit. These ratings can help homeowners select appropriately sized generators for backup power, ensuring they can support essential appliances and electrical needs during power outages.

Remember, it’s always recommended to consult with professionals or refer to specific guidelines for accurate calculations and recommendations regarding kVA and kW ratings in your particular situation.