Hi Lester,Just to clarify, I'm comparing data with the electricity supplier's info (in my case Endeavour), also used by AGL (retailer) for displaying usage so far (and billing); the displayed import and export data always match (ignoring the rounding), but the 'cost to date' value (total cost) doesn't, and in my case, the error cannot be explained with the GST.Note: I believe, solar (battery) systems 'independently' measure your usage (export, import), and there are no guarantees that they will ...