Power gets confusing because different industries settled on different units for the same physical quantity — energy per unit time. Electricians and appliance labels use watts and kilowatts. Engine output is still quoted in horsepower almost everywhere, despite the unit predating the metric system by two centuries. Heating and air conditioning equipment in the US is rated in BTU per hour rather than watts. Generators and electrical supply equipment are rated in kVA, which is not quite the same thing as kW once you account for power factor.
Calculators in this section
The calculators below handle the straightforward unit-to-unit conversions: watts to horsepower, watts to BTU/h, kW to kVA and the reverse of each. Mechanical horsepower (745.7 W) and metric horsepower (735.5 W) are not identical, which is a common source of small discrepancies between a US spec sheet and a European one — worth checking which definition a figure is using before assuming a conversion is wrong.