I use the energy dashboard with my Shelley EM and it works really well. However I want to calculate my monthly bill.
This calculation is pretty simple. Basically:
Bill = Grid_Energy x rate + Grid_Energy_Returned x Feed_in_Tariff + connection_tariff x num_days.
The shelley EM integrates the Import Energy and Export Energy so I just need to remember what that value was at the start of the billing period.
It seems the energy dashboard has all this, but I am not sure how to get it. An example from my energy dashboard for the month is below.
