One thing to consider in this – I have mentioned this elsewhere in solar discussions – electricity is priced in tiers here in SD.
Thus, your paback varies dramatically depending on how much electricity you use.
If you only use the baseline, then you are using solar dollars to buy-down fairly inexpensive electricity.
If you use enough to put you into the third or fourth tier, you are using solar dollars to buy down expensive electricity.
Also, as you install more and more solar capacity, you reduce the marginal effect as you move down through the electricity price tiers.
Pricing to install solar is also tiered. You have to buy panels and equipment to condition the electricity so it can be fed into the grid. The first set of conditioning equipment can handle so many panels (lets say it is 30 panels for example). After that, you need more conditioning capacity. So, the first panel is very expensive because you ahve to buy conditioning equipment for it and the capacity of that equipment is 30 panels. So, to add panels 2 through 30 isn’t so bad. But, the 31st panel is expensive again.
So, you have to really understand how and where the cost tiers of installing match up with the savings tiers of how electricity is priced.
Using solar to replace ALL of your electricity needs may not be optimal. Using solar to drop your usage from a high tier to a low tier may have a much shorter payoff period.
