I am trying to determine the cost of having lots of 277 vac flourescent lights on when not necessary. They are all fed from the 3 phase to neutral legs of of a transformer's wye connected secondary (3 ph. 480/277 delta/wye transformer).

With all the lights on, I measured the following phase-neutral voltages and phase currents with a true rms multimeter and clamp-on style ammeter:

Rich (BB code):

```
Measured Ph. Voltage (vac) Measured Ph. Current (amps)
Phase A - N = 282 Phase A = 91
Phase B - N = 281 Phase B = 88
Phase C - N = 279 Phase C = 93
```

I'm not sure how to calculate the total kW. I assume that the product of my measured values of voltage and current E x I would give the volt-amps for each phase. And multiplying that times the power factor and dividing by 1000 would give the kilowatts for each phase, correct? But, then how do I combine the three phase kW numbers to get the total kW - just add them? - use phasors???

If I call what I measured with my meters,

**E-meas**and

**I-meas**, does the power company's meter (what we're getting billed for) measure the lower valued kWh [(

**E-meas**x

**I-meas**x

**power factor**)/1000 x hrs], or the higher valued kVAh [(

**E-meas**x

**I-meas**)/1000 x hrs]?

I'm just not sure about how to properly total those unbalanced 3-phase loads, and what type of power (real or apparent) the power companies base their charges on.

Thanks a lot for any help with this!