Power

The power is a measure of the rate at which work is done, therefore the underlying units are those of work or energy .Just like the calorie,the horsepower it can take 5 different values, and these are identified as necessary by the addition of (boiler), (electric), (metric), (UK) and (water). Unlike the calorie (whose 5 values are reasonably close to each other), the horsepower has 4 which are close and 1 (boiler) which is considerably different - it is about 13 times bigger than the others - but it seems to be very little used.
The S I unit of power is the watt. To change any of these other units of energy or work into their equivalent values in watts use the operation and conversion factor given. Those marked with * are exact.

Btu/hour		x 0.293 071
Btu/minute		x 17.584 267
Btu/second		x 1055.056
calories/hour		x 0.001 163 *
calories/minute	 	x 0.069 78 *
calories/second		x 4.1868 *
ft lb-force/minute	x 0.022 597
ft lb-force/second	x 1.355 82
gigawatts [GW]		x 1 000 000 000
horsepower (electric)	x 746 *
horsepower (metric)	x 735.499

watts [W]		1

joules/hour		divide by 3600 *
joules/minute		divide by 60 *
joules/second		1
kilocalories/hour	x 1.163
kilocalories/minute	x 69.78
kg-force meters/hour	x 0.002 724
kg-force meters/minute	x 0.163 444
kilowatts [kW]		x 1000 *
megawatts [MW]		x 1 000 000 *