Wagga, by the payback ratio, are you looking at the $104,000 per year saved vs. the $4,400,000 cost?
I guess that does look odd -- Even at zero interest, it would take 42 years to recover the cost.
But then, I put in a system about 1% of that size, and CA paid about 17% of the cost right away, and the IRS paid another 30% on April 15. So it cost me about half the sticker amount. (Aaack! Does that make me a welfare recipient?
And I pay a whole lot (about 3x) more for some of my power than the 13 cents per kwh that their figures show. So with the big discount and the higher cost for power, my payback comes in about 10 years, even with interest. And part of the 10 year payoff comes in where you figure that the cost of power (or inflation) is increasing at about 6%.
Yosemite is sucking power off the same grid, so by solar generating part, it effectively reduces the cost to the rest of the grid by reducing the need build more generating (and CO2 producing) capacity.
And just as an aside, my little system went on-line in November, and has produced 4000 kwh. In January, I had used 900 kwh off the grid. But now, I have replaced all but 200 kwh of that!