The most likely cause for inaccuracy might be because one of your consumption sensors is not located correctly.
Check the LED sensor on your import meter is located over the pulsing LED labelled imp/kwh and make a visual check that this LED pulses when you are consuming electricity from the grid (i.e at night when you are not generating electricity). This will help identify the correct LED. If this LED also pulses during the day when you are generating enough electricity to cover you household consumption (like with the Siemens S2AM meter) you may have an incompatible electricity pulse meter.
Check that the CT sensor is located on the main live incoming cable to your electricity meter. This cable can be identified by colour (red or brown) or by the letter L. It may be that all the cables are grey and you are unsure. In this case you can try each one in turn (perhaps turning a kettle or different appliance on and off each time) to identify the correct cable.
If all of the sensors are installed correctly but you are still experiencing inaccuracies, check the pulse rate on both meters and compare it with the pulse rate configured on your Chorus: » Installation » Network » Meter Sensors » LED Pulse
The pulse rate is usually displayed next to the LED pulse output on a meter. It will be in the following format: 1000 imp/kWh (where 1000 could be any number from 100 to 10,000).
Inverter Output Type
In some cases the inaccuracies may be due to the CT sensor misreading the current being outputted from the PV inverter. This is most apparent when the system is exporting power to the grid.
The CT sensor is calibrated for grid power and to work with the majority of inverters. However, if all of the steps above have failed and the Usage figure is still inaccurate, it is possible the CT sensor is misinterpreting the current being outputted from your inverter.