I don't understand the reasoning behind the thoughts that 240V uses less energy than 120V. Granted resistive losses will be lower in the 240V circuit than 120V, so for longer runs you certainly would want to use the 240V. But for typical residential use 120V seems to be just as efficient as 240V (within less than 1% anyway).
Ignoring power factor, a 120V pump is going to use the same amount of energy (VA 'Volt-Amps') to do the same work as a pump running 240V; the 120V will use more amps than the 240V but the (VA or Watts 'ignoring power factor') will be the same.
The 120V pump:
Volts x Amps = VA (or Watts ignoring power factor)
120 volts x 12 amps = 1440 VA
The 240V pump:
(only needs 6amps to do the same amount of work, BUT the same amount of energy is used)
240 volts x 6 amps = 1440 VA
The 120V pump uses twice the amps, BUT the same amount of watts are used as the 240V pump because the voltage is half of the 240V.
That's my understanding. I'm I wrong on this?