The multimeters monitor voltage and current and of course with those the math for instant power readings and kilowatt hours consumed. Now I can see phase balance and or power input problems, ie. the voltages should be the same or at least with a couple of volts depending on the park wiring loads.
https://www.amazon.com/DROK-200123-Multimeter-Amperage-Voltmeter/dp/B014W3D1OC

