Dictionary of Units / Measurements

# Power Unit

Since power is a measure of the rate at which work is done, the underlying units are those of work or energy, and that section should be looked at for explanations concerning the calorie and Btu. In this section the (IT) values have been used.

In this section it is the horsepower which provides confusion. Just like the calorie, 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. Other values are given to an appropriate degree of accuracy.

 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 metres/hour   x 0.002 724 kg-force metres/minute x 0.163 444 kilowatts [kW]         x 1000 # megawatts [MW]         x 1 000 000 #