Submitted by ausmeerkat on Sat, 2018-02-17 17:17
I've done some analysis of the data reported by the Tesla app vs from my electricity bills, and I've found that my electricity company thinks I'm using about 0.4 to 0.5 kWh more each day than the Tesla app reports. In fact on days when I'm theoretically completely self sufficient (all power usage from solar and battery) I'm always billed a minimum of 0.5 kWh per day. On such days the Tesla app usually only reports 0.1 kWh of grid usage.
Looking at the hour-by-hour breakdown from my electricity retailer, it appears that a small amount of grid power is being used whenever the battery is charging or discharging, but not when it is idle (when the battery is fully charged and excess solar is being exported back to the grid). This seems to imply that the Powerwall is using some grid power that is not reported to the gateway. Does anyone know if this is expected?
I know it's not a huge difference but I'd like to understand what's going on.