I third Iotawatt device as well as ogiewon's driver: [Release] IoTaWatt Power Monitor Driver v0.1.20220103
We had severe undervoltage that I only realized because solar wasn't producing anything on a nice day and I finally figure out the voltage was out of spec so far the inverter shut down. I called power company and the repair guys were amazed I could tell them the voltage from my phone while they're probing the mains with a meter and getting the same #s.
