There are lots of methods, taking the hit up front (which I did), free after ROI achieved (after 5.3 years appx), amortizing the cost over the useful life.
By saying free, I am referring to the variable cost of charging my EV, the variable cost in using my car is therefore nil because it's energy that would otherwise be wasted.
However, I do accept that you are right, it's not really free, but it costs me no more to charge my EV than it would if I didn't.