But why? Assuming for purposes of argument that the only way to get the necessary power in 20 minutes is to use a 99.9% inefficient fusion power plant[*], that explanation presupposes accumulators that has to be filled in 20 minutes. But the accumulators of the
Annic Nova can be filled over a period of six weeks; obviously they can keep the necessary charge over a period of six weeks. So why generate the necessary power in 20 minutes in the first place? Why not have a more efficient power plant (say, a steam engine[**]

) running for a few hours instead? Or why not have the necessary power provided by the starport power grid and kept stored in the accumulators for the 6-8 hours it takes to move out to the jump limit?
[*] Which sounds pretty iffy to me if the amount of power needed is as low as those solar collectors imply, but let that slide.
[**] OK, I don't know how exactly how much solar energy you can collect in a week, but I believe it's a relatively low figure. Perhaps a steam engine wouldn't be able to equal it, but something a good deal less massive than a 99.9% inefficient fusion power plant processing tens of tons of liquid hydrogen should be able to do it. Especially if it has several hours to do it.
Hans