This system got us through the next couple of years, with a 2,500 gallon tank for the house, and another 2,500 gallons added for the garden, at a slightly lower elevation, for faster filling, we were doing well. That is of course when all went well, with interruptions of pumping from silt & air locks, and low flows, we were just keeping up with demand and ending the season with little reserve, and feeling a little vulnerable.
One positive aspect of a direct solar system is that pumping is confined to day light hours and subject to tapering volume as day lengths change, so over pumping of the available source is pretty unlikely.
We successfully worked within our hydro budget, but our tanks were less than full when a little cushion would be nice to have. It was time for the final upgrade. Research revealed the pump we wanted. Together with the needed photovoltaic panel upgrades it seemed an extravagant expense to our shallow capital pool. But, an unexpected gift earmarked for important and durable acquisitions made it feasible, and the Frances Golden ( my paternal Grandmother) Memorial water system was built. Adding to the fund, the perfectly serviceable old pump was sold with its pump house, fittings and filter for a good price .