How to Convert kVA to Amps

What is kVA, and why is it different from kW?

kVA stands for kilovolt-amps; it is a measure of apparent power. kW (kilowatts) is real power, the work actually done. They are related through power factor: kW = kVA × PF.

For purely resistive loads, like electric heaters and incandescent bulbs, power factor is 1, so kVA and kW are equal. For motors, transformers, and much of commercial electrical equipment, power factor is less than 1, and kVA will be larger than kW. Generator and UPS ratings are almost always listed in kVA for this reason.

When you are converting kVA to amps, you are working with apparent power, the total current the wiring and equipment must carry, regardless of how much of that is doing useful work.

The formula

Single-phase: A = (kVA × 1000) ÷ V

Where:

• A = current in amps
• kVA = apparent power in kilovolt-amps
• V = voltage in volts

Steps: (1) Note the kVA rating, from a generator nameplate, UPS spec sheet, or transformer label. (2) Identify the voltage, 120 V, 240 V, or whatever the system voltage is. (3) Multiply kVA by 1000, then divide by voltage.

This formula is for single-phase systems only. Three-phase conversions use a different formula that includes the square root of 3.

Worked examples

Example 1: 5 kVA generator at 240 V

A portable generator rated 5 kVA running at 240 V single-phase.

A = (5 × 1000) ÷ 240 = 20.83 A

That is just under the capacity of a 25 A breaker, or comfortably within a 30 A circuit. This tells you what wire and overcurrent protection the generator's output needs.

Example 2: 3 kVA UPS at 120 V

An uninterruptible power supply (UPS) rated 3 kVA on a 120 V circuit.

A = (3 × 1000) ÷ 120 = 25 A

A 25 A draw at 120 V is substantial; it exceeds a standard 20 A circuit and requires a dedicated 30 A circuit for sustained use.

Example 3: 1 kVA transformer at 240 V

A small single-phase transformer rated 1 kVA at 240 V.

A = (1 × 1000) ÷ 240 = 4.17 A

A relatively modest load, easily handled by a standard 15 A circuit.

Reference table: kVA to amps at 120 V and 240 V (single-phase)

Values are single-phase estimates. Three-phase circuits will produce different current values for the same kVA rating.

When you would use this conversion

kVA shows up most often on equipment that handles large or variable loads: generators, UPS units, transformers, and large HVAC equipment. When you are planning the circuit for any of these, you need to know the expected current draw to size the wire gauge and overcurrent protection correctly.

For example: if a generator is rated 7.5 kVA at 240 V, the formula tells you to expect up to 31.25 A. That sets your minimum wire and breaker size. The 80% continuous load guideline then tells you the practical sustained limit is about 25 A, which is worth checking against your actual expected load.

Note that this conversion assumes the kVA rating is the maximum apparent power. Real load current will be the same or lower depending on actual load power factor.

Related tools and guides

• kVA-to-Amps Calculator, calculate instantly
• Amps-to-kVA Calculator, reverse direction
• Generator Wattage Calculator, estimate backup-load watts before comparing them with generator capacity
• How to Convert kW to Amps
• Running Watts vs Starting Watts
• kW-to-Amps Calculator
• Electricity Basics

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