Does an unbalanced load on a split phase electrical power service affect the power measurement?

Answer 1

I assume you are referring to (in the US) standard 120V/240V single-phase service? The answer is that unbalanced power (more current on one of the hot wires than the other, with resulting neutral current) is a valid condition. Metering for this type of service is designed to measure unbalanced current correctly. Which is a good thing, since just about any home with a toaster or iron plugged in has an unbalanced load to some extent! An example shows how easy this is: We have a 2400W, 240V air conditioner, and a 120W, 120V lamp on the same service. We would expect the meter to measure and bill us for a 2520W demand, right? (2400 + 120 = 2520, or 2.52 kWh per hour) The A/C draws 10A (2400/240=10, ignoring power factor to make the math easier). The lamp draws 1A (120/120=1). So, the meter sees 11A on the black wire, and 10A on the red. We are unbalanced. The meter calculates (or measures mechanically): 11A * 120V = 1320W 10A * 120V = 1200W 1320W + 1200W = 2520W Although there is one amp of neutral current flowing, it doesn't affect our calculations, since the same amp of current is also flowing (and counted) in the black wire. The same principle applies whether we are metering VA or true power (watts).

Answer 2

Yes, an unbalanced load on a split-phase electrical power service can affect the power measurement. The power measurement is calculated based on the current and voltage in the circuit. An unbalanced load means that the current and/or voltage in the different phases of the split-phase system are unequal. This can result in inaccurate power measurements, as the traditional power calculation assumes balanced conditions.