Volts to kW Calculator
Voltage alone doesn't determine power. Combine volts with current (and power factor for AC) to get kilowatts.
Common conversions
| Input | Result |
|---|---|
| 120 V, 10 A (PF 1) | 1.20 kW |
| 120 V, 15 A (PF 1) | 1.80 kW |
| 240 V, 20 A (PF 1) | 4.80 kW |
| 240 V, 30 A (PF 0.9) | 6.48 kW |
| 240 V, 50 A (PF 1) | 12.00 kW |
| 480 V, 25 A (PF 0.85, 1φ) | 10.20 kW |
| 480 V 3φ, 30 A (PF 0.9) | 22.45 kW |
| 12 V DC, 10 A | 0.12 kW |
The math behind it
- kW = 240 × 25 × 0.95 / 1000
- kW = 5,700 / 1000
Everything you need to know
Typing "volts to kW" into a search bar suggests a direct conversion exists, but it doesn't. Voltage measures electrical pressure, not power. Power (kW) depends on how much current flows and, on AC circuits, how efficiently that current does useful work. This calculator asks for voltage, current, and power factor together so the number it returns is real.
Why voltage alone isn't power
Think of voltage as water pressure in a pipe. Pressure alone doesn't tell you how much water is flowing, you also need the flow rate. In electrical terms, current (amps) is the flow rate, and power (kW) is pressure multiplied by flow, adjusted for power factor on AC systems. A 240 V outlet delivering 1 A produces only 0.24 kW, while the same 240 V delivering 40 A produces 9.6 kW. The voltage never changed, only the power did.
Common US voltages: 120V, 240V, 480V
120 V is the standard US household outlet voltage, used for lighting, small appliances, and general receptacles. 240 V comes from combining the two legs of a residential service and powers dryers, ranges, water heaters, and central AC compressors. 480 V is a common commercial and industrial distribution voltage, chosen because it moves the same power with less current than 120 V or 240 V, which means thinner, cheaper wire and lower resistive losses over long cable runs. A 48 kW load needs about 200 A at 240 V but only about 58 A at 480 V three-phase.
Single-phase vs three-phase math
Residential circuits are single-phase: kW = V × A × PF / 1000. Three-phase circuits, common in commercial and industrial buildings, add a √3 (about 1.732) multiplier for line-to-line voltage: kW = √3 × V × A × PF / 1000. Mixing these up is a common sizing error; a 480 V three-phase circuit at 30 A and PF 0.9 delivers about 22.4 kW, not the 12.96 kW the single-phase formula would give.
Common applications
Panels list voltage (120/240 V split-phase in most US homes), but the kW draw of each circuit depends on the connected load's current. Use the breaker's amp rating with the panel voltage to estimate the maximum kW per circuit.
Nameplates often list voltage and rated amps separately. Multiplying them together, with PF, checks the advertised kW output and can catch a mislabeled or counterfeit unit before installation.
Off-grid systems commonly run at 12 V, 24 V, or 48 V DC. A 48 V battery bank supplying 50 A delivers 2.4 kW, four times the power of the same current at 12 V, which is why larger systems use higher DC voltages.
Three-phase motors are commonly rated 208 V, 240 V, or 480 V. Confirming the nameplate current at the supply voltage reveals the real kW draw before you size a breaker or feeder.
Common mistakes
A 240 V circuit isn't automatically a fixed number of kW. Two loads on the same 240 V circuit can draw 1 kW or 10 kW depending on current alone.
Motors, compressors, and ballasts rarely run at PF 1.0. Leaving PF at 1 when the real value is 0.85 overstates true power by roughly 15%.
480 V three-phase circuits need the √3 multiplier. Leaving it out understates delivered power by about 42%.
Voltage can sag several percent under heavy load. For rough sizing that's fine, but for precise readings, measure the actual voltage at the load, not just the nominal supply rating.
Frequently asked questions
Can you convert volts to kW without knowing the current?+
No. Volts measure electrical pressure, not power. You need the current in amps, and power factor for AC, before you can calculate kilowatts, so a volts-only figure has no fixed kW equivalent.
How many kW is 120 volts?+
It depends on current. 120 V at 10 A is 1.2 kW, and the same 120 V at 15 A is 1.8 kW. Voltage alone never fixes the power.
How many kW is 240 volts?+
It also depends on current. 240 V at 20 A is 4.8 kW, and 240 V at 50 A is 12 kW.
How many kW is 480 volts three-phase?+
480 V three-phase at 30 A with PF 0.9 works out to about 22.4 kW, using kW = √3 × V × A × PF / 1000.
Is voltage the same thing as power?+
No. Voltage is electrical pressure measured in volts, and power is the rate of energy transfer measured in watts or kW. You need both voltage and current to know power.
Do I need a power factor for a DC circuit?+
No. DC circuits have no power factor, so the formula simplifies to kW = V × A / 1000 with no PF term at all.
What power factor should I use for household appliances?+
Resistive loads like heaters and incandescent lighting use PF 1.0. Motors, compressors, and fluorescent or LED drivers typically run 0.8 to 0.95; check the nameplate if precision matters.
Why do industrial buildings use 480 V instead of 240 V?+
Higher voltage delivers the same power with less current, which means smaller conductors, lower resistive losses, and cheaper wiring over long industrial runs.
Does three-phase voltage use the same formula as single-phase?+
No. Three-phase line-to-line voltage needs a √3 (about 1.732) multiplier: kW = √3 × V × A × PF / 1000, versus kW = V × A × PF / 1000 for single-phase.