Convert Apparent Power from Millivolt-Amperes to Kilovolt-Amperes (mVA to kVA)

What is a Millivolt-Ampere (mVA)?

A Millivolt-Ampere (mVA) is a unit of measurement for apparent power, formally recognized by the International System of Units (SI).

It is a tiny unit, equal to exactly one-thousandth of a Volt-Ampere (0.001 VA).

Because this unit is so small, it is not used for common household appliances but is instead used to measure the power in low-energy systems.

You will typically find mVA used in specifications for:

• sensitive electronics
• small transformers
• medical devices
• precision sensors

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What Does mVA Measure? (Apparent Power vs. True Power)

The Millivolt-Ampere (mVA) is a unit of apparent power. This is the total power in an AC (alternating current) circuit.

However, it's not the same as the "true power" (measured in Watts) that actually does work, like lighting a bulb.

A simple way to understand this is the "beer analogy":

• True Power (Watts): This is the beer itself—the part you actually want that does the "work."
• Reactive Power (VAR): This is the foam on top. It's not beer, but it's still part of what's in the glass and takes up space.
• Apparent Power (VA or mVA): This is the total of the beer and the foam. It represents the full load the circuit must be able to handle.

Engineers use mVA to precisely measure this total load in very sensitive, low-power circuits.

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How to Convert Millivolt-Amperes (mVA) to Volt-Amperes (VA)

The conversion between mVA and its base unit, the Volt-Ampere (VA), is very straightforward. The prefix "milli" means "one-thousandth."

• 1 mVA = 0.001 VA
• 1,000 mVA = 1 VA

This simple 1,000-to-1 ratio makes it easy to scale measurements.

For example, a small electronic component rated at 250 mVA is drawing 0.25 VA of apparent power.

What is a Kilovolt-Ampere (kVA)?

A Kilovolt-Ampere (kVA) is a unit of measurement for "apparent power."

Apparent power represents the total amount of power being used in an electrical circuit. One kVA is equal to 1,000 volt-amperes.

Think of it as the complete power load, which is why kVA is the most important measurement for correctly sizing heavy-duty electrical equipment.

Apparent power (kVA) is a combination of two distinct types of power:

1. Real Power (kW): This is the "useful" power that performs the actual work, like lighting a bulb or turning a motor.
2. Reactive Power (kVAR): This is the power required by equipment like motors and transformers to create a magnetic field, which is necessary for their operation.

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How to Calculate kVA

You can calculate kVA using a simple formula.

For a single-phase circuit, which is common in most homes and small businesses, the kVA formula is:

kVA = (Voltage × Amperes) / 1000

For example, a 240-volt circuit drawing 50 amps would have an apparent power of 12 kVA.

(240 Volts × 50 Amps) / 1000 = 12 kVA

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Why kVA Matters: Sizing Generators and UPS Systems

This is the most crucial part: Key equipment like generators, transformers, and Uninterruptible Power Supplies (UPS) are all rated in kVA.

This kVA rating tells you the true maximum load the equipment can safely handle.

If you only look at the real power (kW) when sizing a generator or UPS, you risk choosing a unit that is too small.

An undersized unit can overload, overheat, or fail when you need it most.

The kVA rating provides the complete power picture, ensuring your equipment can handle both the "useful" (kW) and "wasted" (kVAR) power safely.