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kW to Amps Calculator
Kilowatts only become amps once you supply a voltage, and the voltage you choose is where nearly all of the errors live.
Kilowatts to current, for single-phase or three-phase supplies.
Amps = (kW × 1000) ÷ (Volts × PF × phase factor)
A 3 kW load draws 25 amps at 120V and 12.5 amps at 240V. To convert kW to amps by hand, multiply kilowatts by 1,000 to get watts, then divide by the voltage the load actually runs at. Motors and compressors need one more division, by power factor.
The formula, and what each term means
Power is voltage multiplied by current, so current is power divided by voltage. Kilowatts are thousands of watts, which is where the 1,000 comes from: amps = (kW × 1,000) ÷ volts.
- Kilowatts are a rate, not an amount. A 1.5 kW kettle draws 1.5 kW while it boils and nothing once it clicks off.
- Volts are the pressure behind the current. This term belongs to the circuit rather than the appliance, and you have to supply it. Nothing about a 3 kW rating tells you what it is.
- Amps are the flow of current, and the unit every protective device is rated in: breakers, fuses, wire gauge, DC ports, charge controllers, battery management systems.
- Power factor applies on AC only: the ratio of real power (kW) to apparent power (kVA), between 0 and 1. Resistive loads sit at 1.0; motors sit lower and pull more current than the simple sum predicts.
kW is not kWh, and that is the mistake which dominates this conversion. Batteries are sold in kilowatt-hours and inverters in kilowatts, so the two get used interchangeably. A 5 kWh battery has no amp figure until you say how fast you intend to take the energy out: at 1 kW it passes about 21 amps from a 48V bank for five hours, and at 5 kW about 104 amps for one. If your number ends in an h, start with watts to kWh.
The second trap is the voltage itself, because one rating gives two answers: 3 kW is 25 amps at 120V and 12.5 amps at 240V. Confirm the voltage at the load rather than assuming the building’s service. A US receptacle is 120V, a range or dryer circuit is 240V, and anything behind an inverter runs at 12V, 24V or 48V on the battery side of the box.
Quick-reference conversion table
Single-phase AC at a power factor of 1.0, correct for heaters, kettles, toasters, hot plates, hair dryers and anything else that is essentially a resistance. The columns are the two standard US mains voltages: 120V for normal receptacles, 240V for large appliance circuits. Motor loads need the correction further down.
| Kilowatts | Watts | Amps at 120V | Amps at 240V |
|---|---|---|---|
| 0.25 kW | 250W | 2.08 A | 1.04 A |
| 0.5 kW | 500W | 4.17 A | 2.08 A |
| 0.75 kW | 750W | 6.25 A | 3.13 A |
| 1 kW | 1,000W | 8.33 A | 4.17 A |
| 1.5 kW | 1,500W | 12.5 A | 6.25 A |
| 2 kW | 2,000W | 16.67 A | 8.33 A |
| 2.5 kW | 2,500W | 20.83 A | 10.42 A |
| 3 kW | 3,000W | 25 A | 12.5 A |
| 3.5 kW | 3,500W | 29.17 A | 14.58 A |
| 4 kW | 4,000W | 33.33 A | 16.67 A |
| 5 kW | 5,000W | 41.67 A | 20.83 A |
| 6 kW | 6,000W | 50 A | 25 A |
| 7.5 kW | 7,500W | 62.5 A | 31.25 A |
| 10 kW | 10,000W | 83.33 A | 41.67 A |
Two lines are worth committing to memory. 1 kW at 120V is 8.33 amps, so an ordinary 15A receptacle circuit is full at 1.8 kW and should not be asked to carry more than 1.44 kW for hours at a time. And 10 kW at 240V is 41.67 amps, which is why whole-home backup equipment so often lands on a 50A circuit.
Why kW to amps matters for portable power and solar
Batteries, inverters and panels are advertised in kilowatts. Almost everything that can stop them working is rated in amps. Sizing a system is a sequence of translations between the two, and the translation is where the money goes.
- Charging a power station from the wall. A unit pulling 2 kW of AC input draws 16.67 amps at 120V, more than a 15A breaker will hold at all and more than a 20A breaker will hold for a long charge. Turning the input down to about 1.4 kW is the fix, and it is gentler on the cells.
- Shore power in an RV. A 30A hookup is 30 amps on one 120V leg, so 3.6 kW for the whole rig including the air conditioner. A 50A hookup is 50 amps across two legs, so 12 kW. Our off-grid RV section covers what fits inside those numbers.
- Solar charge controllers. MPPT units are rated by the current they deliver to the battery, not by array wattage. A 2 kW array into a 48V bank is about 41.7 amps, so a 50A controller covers it. The same array into a 12V bank is about 167 amps, which no single residential controller will take.
Working from a whole load list rather than one figure, add it up in watts, convert the total here, then let the power station finder and the comparison table filter the catalogue by rated continuous output. Units wired into a panel rather than plugged into a socket sit on the home battery backup page, and those are the ones that can take 240V and halve every current here.
The DC side: 12V, 24V and 48V battery current
This is the half generic converters skip, and the half that matters if you are building anything around a battery. Same formula, much lower voltages, currents large enough to decide the hardware.
| Power | Amps at 12V | Amps at 24V | Amps at 48V |
|---|---|---|---|
| 0.1 kW | 8.33 A | 4.17 A | 2.08 A |
| 0.25 kW | 20.83 A | 10.42 A | 5.21 A |
| 0.5 kW | 41.67 A | 20.83 A | 10.42 A |
| 0.75 kW | 62.5 A | 31.25 A | 15.63 A |
| 1 kW | 83.33 A | 41.67 A | 20.83 A |
| 1.5 kW | 125 A | 62.5 A | 31.25 A |
| 2 kW | 166.67 A | 83.33 A | 41.67 A |
| 3 kW | 250 A | 125 A | 62.5 A |
| 4 kW | 333.33 A | 166.67 A | 83.33 A |
| 5 kW | 416.67 A | 208.33 A | 104.17 A |
Use the nominal voltage, not the resting voltage. A pack sags under load, and the current is highest exactly when the battery is lowest, so dividing by 12 rather than 13.2 gives the conservative answer, and the conservative answer is the one to wire for.
These figures also assume perfect conversion. A real inverter is 85–90% efficient, so the current leaving the battery is higher than the table says. Divide by 0.85 for a working number:
- 1 kW of AC output from a 12V system draws about 98 amps, not 83.
- 3 kW from 12V draws about 294 amps.
- 5 kW from 12V draws about 490 amps, which is why that combination is not sold. The same 5 kW from 48V draws about 123 amps: ordinary cable, ordinary fuse.
That is the whole argument for 48V, and it is arithmetic rather than marketing. Doubling the system voltage halves the current, and heating in a conductor rises with the square of the current, so halving the current quarters the loss. The solar sizing guide works through the array side of the same sum.
Do not eyeball DC cable from this table. At 250 amps an undersized run or a loose terminal is a fire rather than a nuisance, and the correct gauge also depends on length, temperature and bundling. Use these numbers to understand the load, and the manufacturer’s manual, local code and a qualified installer to specify the wiring and the fuse.
Power factor and the 80% rule
Power factor, on AC only
For anything with a motor in it, dividing by voltage alone understates the current. The full single-phase formula is amps = (kW × 1,000) ÷ (volts × power factor). Power factor is below 1, so dividing by it makes the answer larger. Taking 1 kW on a 120V circuit:
- Power factor 1.0, a heater or kettle: 8.33 A
- Power factor 0.9, a well-corrected appliance: 9.26 A
- Power factor 0.8, a typical motor: 10.42 A
- Power factor 0.6, a small or lightly loaded motor: 13.89 A
If the load has a motor and the plate states no power factor, use 0.8. It adds 25% to the current, which is the right direction in which to be wrong. DC has no power factor at all, which is why the battery table needs no correction. Three-phase divides by 1.732 as well, putting 1 kW on a 208V three-phase supply at 2.78 amps. One consequence worth knowing: an inverter rated 3 kW may not carry a 3 kW motor load, because inverter ratings assume a power factor near 1.
The 80% rule
A breaker’s printed number is not a budget you may spend in full. A load running three hours or more is limited to 80% of the rating, because sustained current heats the breaker until it trips on temperature rather than on a fault. Battery charging, EV charging, space heating and air conditioning all count as continuous.
| Circuit | Continuous amps | Continuous kW |
|---|---|---|
| 15A at 120V | 12 A | 1.44 kW |
| 20A at 120V | 16 A | 1.92 kW |
| 30A at 120V | 24 A | 2.88 kW |
| 20A at 240V | 16 A | 3.84 kW |
| 30A at 240V | 24 A | 5.76 kW |
| 40A at 240V | 32 A | 7.68 kW |
| 50A at 240V | 40 A | 9.6 kW |
The practical consequence: 3 kW of output cannot live on a 120V receptacle circuit, because 25 amps exceeds even a 20A breaker. The same 3 kW at 240V is 12.5 amps and sits comfortably inside a 20A circuit. Much of the gap between plug-in power stations and hard-wired home batteries is that one line of arithmetic. Everything already on the circuit counts toward the total.
Frequently asked questions
How many amps is 1 kW?
It depends entirely on the voltage. One kilowatt is 8.33 amps at 120V, 4.17 amps at 240V and 83.33 amps on a 12V battery. There is no single answer without a voltage attached, which is why every honest converter asks for one.
How do you convert kW to amps?
Multiply kilowatts by 1,000 to get watts, then divide by the voltage. For single-phase AC with an inductive load, divide once more by the power factor; for three-phase, divide by 1.732 as well. So 2 kW on a 120V circuit is 2,000 divided by 120, or 16.67 amps.
How many amps is 3 kW at 240V?
12.5 amps at a power factor of 1.0. The same 3 kW on a 120V circuit is 25 amps, which is why 3 kW appliances are normally wired at 240V. On a motor at a power factor of 0.8 the 240V figure rises to about 15.6 amps, so a 20A circuit is the sensible minimum.
Is kW the same as kWh?
No, and confusing them is the most common error on this conversion. Kilowatts are a rate of power; kilowatt-hours are an amount of energy. A 5 kW inverter and a 5 kWh battery describe different things, and a kilowatt-hour figure means nothing in amps until you attach a time period to it.
How many amps does a 5 kW inverter draw from a 12V battery?
About 490 amps at full output, allowing for roughly 85% inverter efficiency. That is why 5 kW inverters are not built for 12V systems. The same 5 kW from a 48V bank draws about 123 amps, which ordinary cable and a correctly rated fuse handle. Higher system voltage is the fix, not thicker wire.
What size breaker do I need for a 5 kW load?
At 240V a 5 kW load draws 20.83 amps, and a continuous load may use only 80% of a breaker’s rating, so it needs a 30A circuit rather than a 20A one. At 120V the same load is 41.67 amps and would need 60A, which is why 5 kW loads go on 240V.
Do I need power factor to work out amps?
Only on AC, and only when the load is inductive. Heaters, kettles and resistive elements sit at 1.0, so it changes nothing. Motors, compressors, pumps and air conditioners run at 0.6 to 0.9, and ignoring it understates the current by 10 to 40%. DC circuits have no power factor.
Going the other way. If you already have amps and want power, use amps to watts. If your figure is in watts rather than kilowatts, watts to amps skips the factor of 1,000.