Electricity Unit Converter
Convert watts, kilowatts, horsepower and BTU/h, turn watt-hours into kWh, or solve watts, volts and amps for DC, single-phase and three-phase circuits. Everything runs in your browser, nothing is sent anywhere.
Quick answer: 1 kW = 1,000 W. 1 kWh = 1,000 Wh = 3.6 MJ ≈ 3,412 BTU, and one billing “electricity unit” is 1 kWh. To convert watts to kWh, multiply watts by hours and divide by 1,000. To find amps, divide watts by volts (single-phase AC: also divide by power factor).
Power is the rate of using energy. Convert between W, kW, MW, horsepower, BTU/h and more.
| Unit | Value |
|---|
Energy is power used over time. This is the unit your electricity bill is based on (kWh).
| Unit | Value |
|---|
Pick what you want to find, then enter the other two values. For AC circuits, set the power factor (use 1 if unknown for a simple heater or incandescent bulb).
Turn a device’s power rating and daily use into kWh (electricity units). Add a price per kWh if you want a rough cost. For full bill estimates use our electricity cost calculator.
| Period | kWh (units) | MJ | BTU | Cost |
|---|
Results are calculated, not measured. Check your device nameplate or meter for real figures. Last updated: .
Electrical unit conversion cheat sheet
These are the conversions people look up most. Factors come from the SI definitions and standard engineering constants (see sources at the end).
| From | Equals |
|---|---|
| 1 kW | 1,000 W |
| 1 MW | 1,000 kW = 1,000,000 W |
| 1 kW | ≈ 1.341 hp (mechanical) ≈ 3,412 BTU/h |
| 1 hp (mechanical) | ≈ 745.7 W |
| 1 hp (metric) | ≈ 735.5 W |
| 1 BTU/h | ≈ 0.2931 W |
| 1 ton of cooling | 12,000 BTU/h ≈ 3.517 kW |
| From | Equals |
|---|---|
| 1 Wh | 3,600 J = 0.001 kWh |
| 1 kWh (1 electricity unit) | 1,000 Wh = 3.6 MJ ≈ 3,412 BTU |
| 1 MWh | 1,000 kWh |
| 1 BTU | ≈ 1,055 J ≈ 0.000293 kWh |
| 1 US therm | 100,000 BTU ≈ 29.3 kWh |
Electricity formulas used by this converter
Power and energy
- Energy (Wh) = power (W) × time (h)
- Energy (kWh) = power (W) × time (h) ÷ 1,000
- Cost = kWh × price per kWh
Watts, volts and amps
| Circuit | Watts | Amps |
|---|---|---|
| DC | W = V × A | A = W ÷ V |
| AC single-phase | W = V × A × PF | A = W ÷ (V × PF) |
| AC three-phase | W = √3 × V × A × PF | A = W ÷ (√3 × V × PF) |
V is voltage, A is current in amps, PF is power factor (a number between 0 and 1). For three-phase, V is the line-to-line voltage. Apparent power in VA is V × A (single-phase) or √3 × V × A (three-phase), and watts = VA × PF.
Worked examples
Example 1: Watts to kWh
A 100 W bulb runs 10 hours a day. Energy per day = 100 × 10 ÷ 1,000 = 1 kWh. Over 30 days that is 30 kWh, or 30 electricity units.
Example 2: Watts to amps (single-phase)
A 1,500 W space heater on a 120 V circuit with PF = 1 draws 1,500 ÷ 120 = 12.5 A. On a 240 V circuit the same heater draws 6.25 A.
Example 3: Three-phase current
A 10 kW motor load on 400 V three-phase with PF = 0.9: current = 10,000 ÷ (1.732 × 400 × 0.9) ≈ 16.0 A per phase.
Example 4: kWh to BTU
A resistive heater that uses 2 kWh produces about 2 × 3,412 = 6,824 BTU of heat.
All examples use round, illustrative numbers. Real appliances vary by model and settings.
What is an “electricity unit”?
On a utility bill, one unit of electricity is one kilowatt-hour (kWh): the energy used by a 1,000-watt load running for one hour. United States bills normally show “kWh” directly. In several other countries, bills and everyday speech say “units” for the same thing. The converter treats 1 unit = 1 kWh.
That is why you will see searches such as “electricity unit to watt”. A unit is energy and a watt is power, so you need a time period to convert between them: 1 unit = 1,000 W used for 1 hour (or 100 W for 10 hours).
Common mistakes when converting electrical units
- Mixing up kW and kWh. kW is how fast power is used right now. kWh is how much was used over time. Bills charge for kWh.
- Converting watts to amps without voltage. The same wattage draws half the current at double the voltage, so the voltage must be known.
- Treating VA as watts. For motors, power supplies and other non-resistive loads the power factor is below 1, so watts are lower than VA.
- Using peak ratings as average use. A fridge compressor or heater thermostat cycles on and off. Running hours are usually less than clock hours.
- Mixing horsepower types. Mechanical (745.7 W) and metric (735.5 W) horsepower differ slightly. Check which one a spec sheet uses.
Limits and safety
Not for wiring decisions. This tool converts units and estimates current. It does not size wires, breakers or fuses, which depends on local electrical code, wire material, temperature, installation method and load type. Use a licensed electrician for that work.
Three-phase results assume a balanced load and line-to-line voltage. Starting current of motors, inrush current and harmonics are not modelled.
Frequently asked questions
What is an electricity unit?
In billing, one electricity unit is one kilowatt-hour (kWh), the energy used by a 1,000-watt load running for one hour. US bills print kWh directly, while many other countries call the same amount a unit.
How do I convert watts to kWh?
Multiply watts by hours of use and divide by 1,000. For example, a 100 W device running for 10 hours uses 100 x 10 / 1,000 = 1 kWh.
How do I convert watts to amps?
For DC, divide watts by volts. For single-phase AC, divide watts by volts times power factor. For example, 1,200 W at 120 V with a power factor of 1 draws 10 A.
What is the difference between kW and kWh?
A kilowatt (kW) measures power, the rate at which energy is used at a moment. A kilowatt-hour (kWh) measures energy, the amount used over time. A 2 kW heater running for 3 hours uses 6 kWh.
How many watts are in one horsepower?
One mechanical horsepower equals about 745.7 watts. One metric horsepower equals about 735.5 watts.
How many BTU are in one kWh?
One kilowatt-hour equals about 3,412 BTU (International Table BTU), or exactly 3.6 megajoules.
What is the difference between VA and watts?
VA is apparent power, volts times amps. Watts is real power, which equals VA times the power factor. For purely resistive loads such as a basic heater the power factor is close to 1, so VA and watts are nearly equal.
Can I use this converter to size wires or breakers?
No. It converts units and estimates current, but wire and breaker sizing depends on local electrical code, load type, wire material, temperature and installation method. Ask a licensed electrician for that.
Sources and method
Conversion factors use SI definitions (1 Wh = 3,600 J, 1 kWh = 3.6 MJ) and standard constants: mechanical horsepower 745.69987 W, metric horsepower 735.49875 W, International Table BTU 1,055.05585 J, thermochemical calorie 4.184 J, US therm 105,480,400 J. Formulas for single-phase and three-phase power are standard AC circuit relationships.
- NIST Special Publication 811: Guide for the Use of the International System of Units
- U.S. Energy Information Administration: Units and calculators explained
Reviewed against the sources above on October 25, 2026. Spotted an error? Tell us and we will correct and re-date the page.
Electricity Unit Converter
Convert watts, kilowatts, horsepower and BTU/h, turn watt-hours into kWh, or solve watts, volts and amps for DC, single-phase and three-phase circuits. Everything runs in your browser, nothing is sent anywhere.
Quick answer: 1 kW = 1,000 W. 1 kWh = 1,000 Wh = 3.6 MJ ≈ 3,412 BTU, and one billing “electricity unit” is 1 kWh. To convert watts to kWh, multiply watts by hours and divide by 1,000. To find amps, divide watts by volts (single-phase AC: also divide by power factor).
Power is the rate of using energy. Convert between W, kW, MW, horsepower, BTU/h and more.
| Unit | Value |
|---|
Energy is power used over time. This is the unit your electricity bill is based on (kWh).
| Unit | Value |
|---|
Pick what you want to find, then enter the other two values. For AC circuits, set the power factor (use 1 if unknown for a simple heater or incandescent bulb).
Turn a device’s power rating and daily use into kWh (electricity units). Add a price per kWh if you want a rough cost. For full bill estimates use our electricity cost calculator.
| Period | kWh (units) | MJ | BTU | Cost |
|---|
Results are calculated, not measured. Check your device nameplate or meter for real figures. Last updated: .
Electrical unit conversion cheat sheet
These are the conversions people look up most. Factors come from the SI definitions and standard engineering constants (see sources at the end).
| From | Equals |
|---|---|
| 1 kW | 1,000 W |
| 1 MW | 1,000 kW = 1,000,000 W |
| 1 kW | ≈ 1.341 hp (mechanical) ≈ 3,412 BTU/h |
| 1 hp (mechanical) | ≈ 745.7 W |
| 1 hp (metric) | ≈ 735.5 W |
| 1 BTU/h | ≈ 0.2931 W |
| 1 ton of cooling | 12,000 BTU/h ≈ 3.517 kW |
| From | Equals |
|---|---|
| 1 Wh | 3,600 J = 0.001 kWh |
| 1 kWh (1 electricity unit) | 1,000 Wh = 3.6 MJ ≈ 3,412 BTU |
| 1 MWh | 1,000 kWh |
| 1 BTU | ≈ 1,055 J ≈ 0.000293 kWh |
| 1 US therm | 100,000 BTU ≈ 29.3 kWh |
Electricity formulas used by this converter
Power and energy
- Energy (Wh) = power (W) × time (h)
- Energy (kWh) = power (W) × time (h) ÷ 1,000
- Cost = kWh × price per kWh
Watts, volts and amps
| Circuit | Watts | Amps |
|---|---|---|
| DC | W = V × A | A = W ÷ V |
| AC single-phase | W = V × A × PF | A = W ÷ (V × PF) |
| AC three-phase | W = √3 × V × A × PF | A = W ÷ (√3 × V × PF) |
V is voltage, A is current in amps, PF is power factor (a number between 0 and 1). For three-phase, V is the line-to-line voltage. Apparent power in VA is V × A (single-phase) or √3 × V × A (three-phase), and watts = VA × PF.
Worked examples
Example 1: Watts to kWh
A 100 W bulb runs 10 hours a day. Energy per day = 100 × 10 ÷ 1,000 = 1 kWh. Over 30 days that is 30 kWh, or 30 electricity units.
Example 2: Watts to amps (single-phase)
A 1,500 W space heater on a 120 V circuit with PF = 1 draws 1,500 ÷ 120 = 12.5 A. On a 240 V circuit the same heater draws 6.25 A.
Example 3: Three-phase current
A 10 kW motor load on 400 V three-phase with PF = 0.9: current = 10,000 ÷ (1.732 × 400 × 0.9) ≈ 16.0 A per phase.
Example 4: kWh to BTU
A resistive heater that uses 2 kWh produces about 2 × 3,412 = 6,824 BTU of heat.
All examples use round, illustrative numbers. Real appliances vary by model and settings.
What is an “electricity unit”?
On a utility bill, one unit of electricity is one kilowatt-hour (kWh): the energy used by a 1,000-watt load running for one hour. United States bills normally show “kWh” directly. In several other countries, bills and everyday speech say “units” for the same thing. The converter treats 1 unit = 1 kWh.
That is why you will see searches such as “electricity unit to watt”. A unit is energy and a watt is power, so you need a time period to convert between them: 1 unit = 1,000 W used for 1 hour (or 100 W for 10 hours).
Common mistakes when converting electrical units
- Mixing up kW and kWh. kW is how fast power is used right now. kWh is how much was used over time. Bills charge for kWh.
- Converting watts to amps without voltage. The same wattage draws half the current at double the voltage, so the voltage must be known.
- Treating VA as watts. For motors, power supplies and other non-resistive loads the power factor is below 1, so watts are lower than VA.
- Using peak ratings as average use. A fridge compressor or heater thermostat cycles on and off. Running hours are usually less than clock hours.
- Mixing horsepower types. Mechanical (745.7 W) and metric (735.5 W) horsepower differ slightly. Check which one a spec sheet uses.
Limits and safety
Not for wiring decisions. This tool converts units and estimates current. It does not size wires, breakers or fuses, which depends on local electrical code, wire material, temperature, installation method and load type. Use a licensed electrician for that work.
Three-phase results assume a balanced load and line-to-line voltage. Starting current of motors, inrush current and harmonics are not modelled.
Frequently asked questions
What is an electricity unit?
In billing, one electricity unit is one kilowatt-hour (kWh), the energy used by a 1,000-watt load running for one hour. US bills print kWh directly, while many other countries call the same amount a unit.
How do I convert watts to kWh?
Multiply watts by hours of use and divide by 1,000. For example, a 100 W device running for 10 hours uses 100 x 10 / 1,000 = 1 kWh.
How do I convert watts to amps?
For DC, divide watts by volts. For single-phase AC, divide watts by volts times power factor. For example, 1,200 W at 120 V with a power factor of 1 draws 10 A.
What is the difference between kW and kWh?
A kilowatt (kW) measures power, the rate at which energy is used at a moment. A kilowatt-hour (kWh) measures energy, the amount used over time. A 2 kW heater running for 3 hours uses 6 kWh.
How many watts are in one horsepower?
One mechanical horsepower equals about 745.7 watts. One metric horsepower equals about 735.5 watts.
How many BTU are in one kWh?
One kilowatt-hour equals about 3,412 BTU (International Table BTU), or exactly 3.6 megajoules.
What is the difference between VA and watts?
VA is apparent power, volts times amps. Watts is real power, which equals VA times the power factor. For purely resistive loads such as a basic heater the power factor is close to 1, so VA and watts are nearly equal.
Can I use this converter to size wires or breakers?
No. It converts units and estimates current, but wire and breaker sizing depends on local electrical code, load type, wire material, temperature and installation method. Ask a licensed electrician for that.
Sources and method
Conversion factors use SI definitions (1 Wh = 3,600 J, 1 kWh = 3.6 MJ) and standard constants: mechanical horsepower 745.69987 W, metric horsepower 735.49875 W, International Table BTU 1,055.05585 J, thermochemical calorie 4.184 J, US therm 105,480,400 J. Formulas for single-phase and three-phase power are standard AC circuit relationships.
- NIST Special Publication 811: Guide for the Use of the International System of Units
- U.S. Energy Information Administration: Units and calculators explained
Reviewed against the sources above on October 25, 2026. Spotted an error? Tell us and we will correct and re-date the page.