I have a tariff the electricity board pay on my solar panel. The tariff is 0.413 cents/kWh. It rises by q=2.4% each year. The system generates power P = 1785 kWh in the first year, going down by d= 0.5% each year (as its cells decay).
I want one formula that works out the total cumulative income after n years.
I've seen an incorrect answer on another board.