Convert Apparent Power from Volt-Amperes to Millivolt-Amperes (VA to mVA)

What is a Volt-Ampere (VA)?

A Volt-Ampere (VA) is a unit of measurement for "apparent power" in an electrical circuit.

It represents the total power supplied by a source, which is critical for understanding a device's full electrical load.

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Understanding Apparent Power vs. Real Power

Think of VA as the total potential power a device can draw.

In contrast, Watts (W) measures the actual working power the device consumes.

This is the key difference between "apparent power" (VA) and "real power" (Watts). The VA rating is always greater than or equal to the wattage.

The difference between these two measurements is known as the "power factor (PF)."

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Why VA is Used for Sizing Equipment

The VA rating is crucial for correctly sizing equipment like uninterruptible power supplies (UPS) and transformers.

Why? Because these devices must support the entire electrical load—which includes both real and reactive power—not just the power being actively used.

Sizing a UPS based only on Watts could lead to overloading and system failure, as it wouldn't account for the total current the connected devices draw.

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The Simple Calculation for Volt-Amperes

The formula to calculate Volt-Amperes is straightforward:

VA = Volts $\times$ Amperes

By multiplying a device's operating voltage by the current (in amps) it draws, you can determine its apparent power.

This calculation is essential for IT professionals and electricians when assessing power needs or planning for new hardware.

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.