Grid charging price limit

[inotkoski-cpu]

The "Grid charging active time" chart does not follow the set price limit when an optional charge and tax are enabled.

I prefer to use the optional charge and tax settings for an accurate charge session price calculation. However, when these are set, the grid charging active time chart becomes misleading: the price limit follows the spot price, but the chart calculates the active time based on the total price (which includes the optional charge and tax).