Power Unit Converter

How to use this calculator

Three inputs. The result shows 5 outputs simultaneously.

Power Value is the number you’re converting. Type it in. Decimals work; so do large numbers for industrial or generation-scale power.

From unit is your source unit. Options: Watt (W), Kilowatt (kW), Megawatt (MW), Gigawatt (GW), Horsepower (HP), Metric Horsepower (PS), BTU/hour (BTU/hr), and Milliwatt (mW).

To unit is your target. Same list.

Click Convert and the blue results panel shows 5 simultaneous outputs: Watts, Kilowatts, Horsepower, BTU/hour, and Energy if run 24 hours (kWh). That last output is the most practically useful one the calculator adds. Power tells you the rate; the 24-hour kWh tells you how much energy that rate consumes or produces in a day, which maps directly to electricity costs.

Power vs energy: the distinction that matters

Power and energy get confused constantly because electricity bills show both.

Power is a rate: how fast energy is being used or generated right now. Measured in watts (W) or kilowatts (kW). A 2,000W electric kettle uses energy at the rate of 2 kW while it’s on.

Energy is the total amount used over time. Measured in kilowatt-hours (kWh). That same 2 kW kettle, if left on for 1 hour, would use 2 kWh of energy. Your electricity bill charges you per kWh.

The relationship:

This is why the calculator outputs “energy if run 24 hours.” Multiply that by your electricity rate and you have the daily cost of running that appliance or device continuously.

A watt is a snapshot. A kilowatt-hour is what you actually pay for. Power tells you the rate of consumption; energy tells you the bill.

The formulas

All conversions go through watts as the base unit.

The energy output formula:

The BTU/hour conversion uses the thermochemical BTU: 1 BTU = 1,055.06 joules, so 1 BTU/hr = 1,055.06 J / 3,600 s = 0.29307 W.

Watts to all power units: full conversion table

Watts (W)	kW	HP (mech.)	BTU/hr	24-hr kWh	Context
1	0.001	0.00134	3.41	0.024	LED bulb
5	0.005	0.0067	17.1	0.12	Phone charger
10	0.010	0.0134	34.1	0.24	Small LED desk lamp
60	0.060	0.0805	205	1.44	Old incandescent bulb
100	0.100	0.134	341	2.40	Bright LED equivalent
300	0.300	0.402	1,024	7.20	Small space heater (low)
500	0.500	0.671	1,706	12.0	Refrigerator (average)
745.7	0.746	1.0	2,545	17.9	Exactly 1 HP
1,000	1.0	1.341	3,412	24.0	1 kW space heater
1,500	1.5	2.011	5,118	36.0	Typical kettle or toaster
2,000	2.0	2.682	6,824	48.0	Electric kettle (large)
3,000	3.0	4.023	10,236	72.0	Electric oven (average)
5,000	5.0	6.705	17,060	120	Residential solar panel array
7,460	7.46	10.0	25,450	179	10 HP motor
10,000	10	13.41	34,121	240	EV fast charger (Level 2)

Horsepower to kilowatts: the automotive range

The conversion most used when comparing car specifications across markets. European specs use kW; US and UK specs use HP.

HP (mech.)	kW	PS (metric)	BTU/hr	24-hr kWh
50	37.3	50.7	127,284	895
75	55.9	75.6	190,927	1,342
100	74.6	101.4	254,566	1,790
120	89.5	121.7	305,479	2,148
150	111.9	152.0	381,849	2,685
200	149.1	203.4	509,132	3,579
250	186.4	253.5	636,415	4,474
300	223.7	304.1	763,698	5,369
400	298.3	405.5	1,018,264	7,158
500	372.9	506.9	1,272,830	8,948
600	447.4	608.2	1,527,396	10,737
750	559.3	760.3	1,909,245	13,422

BTU/hr to watts and kilowatts: HVAC range

HVAC and air conditioning equipment in the US is rated in BTU/hr. This is the table contractors reach for when comparing US and SI specs.

BTU/hr	Watts	kW	HP	Tonnes of refrigeration
1,000	293.1	0.293	0.393	0.083
2,000	586.1	0.586	0.786	0.167
3,000	879.2	0.879	1.179	0.250
5,000	1,465	1.465	1.965	0.417
6,000	1,758	1.758	2.358	0.500
8,000	2,344	2.344	3.143	0.667
10,000	2,931	2.931	3.930	0.833
12,000	3,517	3.517	4.715	1.0
18,000	5,275	5.275	7.074	1.5
24,000	7,034	7.034	9.432	2.0
36,000	10,551	10.55	14.15	3.0
48,000	14,067	14.07	18.87	4.0
60,000	17,584	17.58	23.58	5.0

12,000 BTU/hr = 1 tonne of refrigeration = 3.517 kW. This is the baseline unit for air conditioning capacity. A “2-tonne” AC unit has 24,000 BTU/hr of cooling capacity.

Power reference points: real-world scale

Numbers to calibrate whether a converted value makes physical sense.

Device / source	Power	kW	HP
Human body (resting)	80 W	0.08	0.107
LED light bulb	8-15 W	0.008-0.015	0.011-0.020
Laptop computer	45-65 W	0.045-0.065	0.060-0.087
Desktop computer	150-400 W	0.15-0.4	0.20-0.54
Microwave oven	700-1,200 W	0.7-1.2	0.94-1.61
Electric kettle	1,500-3,000 W	1.5-3.0	2.0-4.0
Hair dryer	1,000-2,000 W	1.0-2.0	1.34-2.68
Residential AC unit	1,000-5,000 W	1-5	1.3-6.7
Electric car (charging, Level 2)	7,200-22,000 W	7.2-22	9.7-29.5
Small car engine	60,000-85,000 W	60-85	80-114
Performance car engine	300,000-600,000 W	300-600	402-805
Residential solar array (avg)	4,000-10,000 W	4-10	5.4-13.4
Wind turbine (onshore)	2-3 MW	2,000-3,000	2,682-4,023
Nuclear power plant (unit)	1,000-1,600 MW	1,000,000-1,600,000	—
Average US household consumption	~1,200 W average	1.2	1.61

Real-world examples

Appliance running cost

A 2,000W electric kettle. How much does it cost to run for 10 minutes per day for a month? Electricity rate: $0.15/kWh.

Comparing car power across markets

A German car is listed as 200 kW. A US review says the same car makes 268 HP. Are they the same?

Solar panel output to household coverage

A 6 kW rooftop solar installation. How many kWh does it produce in a day at average 4.5 peak sun hours? How does that compare to average household use?

Air conditioning size check

A room is 25 m² (about 270 sq ft). A rule of thumb for temperate climates is 60 BTU/hr per square foot. What size AC unit is needed in kW?

Common mistakes people make

Confusing power and energy on electricity bills. Your bill charges in kWh (energy), not kW (power). A 3 kW appliance running for 2 hours uses 6 kWh. People often quote their electricity usage in kW (“my bill says I used 500 kW this month”) when they mean kWh. Power is the rate; energy is the total. Bills measure energy.

Mixing mechanical and metric horsepower. A US car’s HP rating uses mechanical (imperial) horsepower: 1 HP = 745.7 W. European car specs often use PS (Pferdestärke, metric horsepower): 1 PS = 735.5 W. They’re close but not identical. A car listed at 200 PS in Germany is 197.4 HP in the US, not 200 HP. For casual comparison this is negligible. For precise spec matching it matters.

Misunderstanding BTU vs BTU/hr. BTU (British Thermal Unit) is a unit of energy, not power. BTU/hr is power. AC units and furnaces are rated in BTU/hr. When someone says “a 12,000 BTU air conditioner,” they mean 12,000 BTU per hour. The calculator converts BTU/hr (a power unit), not BTU (an energy unit).

Underestimating standby power. Devices in standby mode still draw power: typically 0.5-5W each. A home with 20 devices on standby drawing an average of 2W each uses 40W continuously = 0.96 kWh/day = 350 kWh/year. At $0.15/kWh that’s $52 per year in standby power alone. Small watts add up over 8,760 hours per year.

Assuming generator wattage is continuous output. Portable generators are rated in peak (surge) watts and continuous (running) watts. A “3,000W generator” might deliver 3,000W peak but only 2,500W continuously. Size your load against the continuous rating, not the peak.

Power in context: orders of magnitude

Scale	Power range	Examples
Microwatts	1-1,000 µW	Wireless sensor, pacemaker battery
Milliwatts	1-1,000 mW	Bluetooth transmitter, watch battery
Watts	1-1,000 W	Phones, laptops, bulbs, appliances
Kilowatts	1-1,000 kW	HVAC, vehicles, industrial motors
Megawatts	1-1,000 MW	Power stations, large factories
Gigawatts	1-1,000 GW	National grid, large power regions
Terawatts	1+ TW	Global energy consumption (~19 TW)

Power, voltage, and current: how they connect

Power conversion often comes up alongside electrical calculations. The relationship between power, voltage, and current:

Power (watts) equals voltage (volts) times current (amperes). This means:

A 1,000W appliance on a 120V circuit draws 1,000 / 120 = 8.33 amps. The same appliance on a 240V circuit draws 4.17 amps. Same power, half the current. This is why high-power appliances (ovens, EV chargers, dryers) use 240V in homes: lower current means thinner wires and less heat loss.

For three-phase industrial power, the formula adjusts:

The power converter handles watt-to-watt conversions. For V-I-P calculations, use a dedicated electrical calculator alongside this one.

The bottom line

Power units split across two worlds: electrical (watts, kilowatts) and mechanical (horsepower). They’re measuring the same thing at different scales and in different industries. The BTU/hr unit adds a third world: HVAC and thermal engineering.

The calculator shows all equivalents at once and adds the 24-hour kWh output, which is the one number that connects power to actual cost. Enter your power value, read the conversions, and use the kWh figure to calculate daily energy consumption.

For anything involving running costs: kWh is what the meter measures. Watts is just how fast you’re filling it up.