Yeah it comes down to energy density and time to replace expended energy. That's why the most successful electric trucks i've seen basically go to a depot where the entire battery pack is swapped out for a pre-charged one.
Of course there's a whole other piece of calculus that is ignored in New Zealand - and that is energy efficiency. Reducing the size of, and need for, long distance trucking by utilising far more fuel efficient rail & coastal shipping would also reduce emissions; and would allow us to decrease maintenance and new build costs for roads.