Hello, I've been playing around with this a little and I think it might be beneficial to the forecast model to add the electricity price to the dataset. (if I have this right, this is a "future regressor" in neuralprophet speak)
There should be some correlation between electricity price and load. This may negate the need to manually subtract the car charging load, as it will learn that these heavy loads only occur in times of lower electricity prices, which in turn will stop it forecasting heavy load where there has been past free electricity/power-up or daytime IOG slots.