Need source for voltmeter with rs232 output

[Xetonett]

has anyone used or have seen a voltmeter that can be mounted with the HA equipment, monitor the AC power, and then send the reading via rs232 to a pc? I am doing a job and Florida (I am in PA) and i want to monitor the voltage feeding the equipment in case there is a issue that needs troubleshooted.
Am looking for a slightly bigger unit and possible the residential refrigerator. Has anyone put a Kill a Watt meter on the Frigidaire residential refrigerator to see what is the kWh usage per day? Looking at the Energy Guide for that model, it estimates 688 kWh per year or 1.88 kWh per day, I found one here https://refrigeratorfaq.com/how-many-am ... rator-use/. This converts to 157 Ah per day, I think. Seems high to me if running off batteries and inverter for a short period of time, like a day. Most of what I've read suggest a residential refrigerator should use about 1 kWh per day when sizing for solar and batteries. If you had 4 6v batteries, the refrigerator would use over 3/4 of your Ah capacity per day. I may be looking at this wrong. Just wondering if anyone has actually measured kWh with a Kill a Watt mater.