For the better part of the last century, we measured electrical work in Watts. It was a simple and good life! Volts times Amps equaled Watts! It is sad to report that our friend has passed on as an accurate measurement. Mr Watt is survived by his brother VA. "What?", you say, "I didn't even know he was ill!" It is a long and sad story that started with the introduction of electronic equipment, and has spread to larger devices, such as electronic ballast systems. Most all of these devices change power from ac to dc and store them in a capacitor which then feeds switch-mode power supplies and other circuitry. In the process, something strange happens: No power flows in the primary circuit until the waveform voltage of the ac line exceeds the current voltage in the supply capacitor. The Diode blocks it. In other words, the only part of the AC waveform that is doing any work is the portion near the peak voltage. In calculating wiring loads, the Watt no longer works as it is based on a liner draw of power across the full waveform. Now, part of the waveform is left dead, and the peak of the waveform draws an unexpectedly high value of current. To try to rate this draw, a new term came out called VA. Anybody who has dealt with battery back-up supplies or computer power supplies knows the plates rate them in VA and the VA number is higher than the wattage draw of the unit. "What is VA then? Isn't it Volts times Amps?", you may ask. Nope! VA is the calculated voltage multiplied by the maximum waveform draw. Since all of the work is being done during only part of the waveform, the VA value must be used to calculate wiring and power source capacity requirements. Wire works like a big resistor. If your 575 watt mover is drawing 7 amps during part of the waveform, it may still be considered a 575 watt load, but power distribution must be handled based on the 7 amp draw, or wiring voltage drop may become a problem. This is not to be confused with strike and startup draw, which requires even more current. 7 amps would be the running draw. (Also, this should not be confused with "Power Factor" which is a whole other subject!) "Huh? 120 times 7 equals 840? Why is it drawing so many watts?", you may ask. Its not! Confused? The ballast is only drawing 575 watts, plus a few for itself. (Maybe 625 total) But.... the VA draw is 840VA. The reason there is a difference is that there is a portion of the waveform where the fixture is drawing nothing! So, for wattage, you have to calculate the VA draw, then prorate it by the percentage of the waveform the draw is occurring over. (Kind of a pain) For power distribution, we can only be concerned with the VA rating, making the watt obsolete! I loved Mr Watt. He was married to Mrs Incandescent, who I fear is not doing well either. Both lived in the town of Resistance-ville, but I hear that is being demolished to make way for the new community of Inductor City.