Specifications

The Difference Between Watts and VA
Question: Why are the required Watts and VA so different?
Answer: Watts is a scalar quantity which is frequently used to measure system efficiency. It is the energy supplied
by the utility company over a given period of time and is commonly referred to as power. Except for heavy industrial
users, the utility company only bills users for the watts consumed. Watts are directly convertible into mechanical
work or BTUs (British Thermal Units) of heat. Wasted power is paid for a second time in terms of additional loading
on the user's air-conditioning system. Mathematically, it is a scalar quantity resulting from the vector product of two
vector quantities (volts and amps). It is NOT the simple algebraic product of the rms volts times rms current.
VA on the other hand IS the scalar quantity resulting from multiplying the magnitudes (rms) of the vector quantities
(volts and amps). This resulting quantity will never be smaller than the watts demanded by an instrument.
Uninformed users incorrectly use VA to assess the device's over-all efficiency and power demands. VA is most
frequently and correctly used by electricians to determine proper ac mains conductor gage and circuit breaker sizing.