Power calculation

Watt definition

 

Watt is the unit of power (symbol: W).

The watt unit is named after James Watt, the inventor of the steam engine.

One watt is defined as the energy consumption rate of one joule per second.

1W = 1J / 1s

One watt is also defined as the current flow of one ampere with voltage of one volt.

1W = 1V × 1A

Kilowatt-hour definition

Kilowatt-hour is an energy unit (symbol kWh or kW•h).

One kilowatt-hour is defined as the energy consumed by power consumption of 1kW during 1 hour:

1 kWh = 1kW • 1h

One kilowatt-hour is equal to 3.6•10⁶ joules:

1 kWh = 3.6•10⁶ J

The energy E in kilowatt-hour (kWh) is equal to the power P in kilowatts (kW), times the time t in hours (h).

E_(kWh) = P_(kW) • t_(h)

Table of unit prefixes of watt

name	symbol	conversion	example
picowatt	pW	1pW = 10-12 W	P = 10 pW
nanowatt	nW	1nW = 10-9 W	P = 10 nW
microwatt	μW	1μW = 10-6 W	P = 10 μW
milliwatt	mW	1mW = 10-3 W	P = 10 mW
watt	W	-	P = 10 W
kilowatt	kW	1kW = 103 W	P = 2 kW
megawatt	MW	1MW = 106 W	P = 5 MW
gigawatt	GW	1GW = 109 W	P = 5 GW

convert watts to kilowatts

The power P in kilowatts (kW) is equal to the power P in watts (W) divided by 1000:

P _(kW) = P _(W) / 1000

convert watts to milliwatts

The power P in milliwatts (mW) is equal to the power P in watts (W) times 1000:

P_(mW) = P_(W) • 1000

convert watts to dBm

The power P in decibel-milliwatts (dBm) is equal to 10 times base 10 logarithm of the power P in milliwatts (mW) divided by 1 milliwatt:

P_(dBm) = 10 • log₁₀( P_(mW) / 1mW)

convert watts to amps

The current I in amperes (A) is equal to the power P in watts (W) divided by the voltage V in volts (V):

I_(A) = P_(W) / V_(V)

convert watts to volts

The voltage V in volts (V) is equal to the power P in watts (W) divided by the current I in amperes (A):

V_(V) = P_(W) / I_(A)

convert watts to ohms

R_(Ω) = P_(W) / I_(A)²

R_(Ω) = V_(V)²/ P_(W)

convert watts to btu/hr

P_(BTU/hr) = 3.412142 • P_(W)

convert watts to joules

E_(J) = P_(W) • t_(s)

convert watts to horsepower

P_(HP) = P_(W) / 746

convert watts to kVA

The real power P in watts (W) is equal to 1000 times the apparent power S in kilo-volt-amperes (kVA) times the power factor (PF) or cosine of the phase angle φ:

P_(W) = 1000 • S_(kVA) • PF = 1000 • S_(kVA) • cos φ

convert watts to VA

The real power P in watts (W) is equal to the apparent power S in volt-amperes (VA) times the power factor (PF) or cosine of the phase angle φ:

P_(W) = S_(VA) • PF = S_(VA) • cos φ