The utility companies try to keep it to ±5%
The voltage goes above or below those limits at times, but typically for relatively short periods,
e.g. a few hours.
i v had a good at this charger, it seem a far more versitile tool than the EU version and i think it would work well for me. Does it connect to the Emonpi for solarPV monitoring?
Yes, it runs the same OpenEVSE WiFi software. We develop it in collaboration with OpenEVSE.