Check out the updated PV Cash Flow Worksheet over in the “Resources for Energy Nerds” page on my site. This calculator shows a cash-flow comparison between a theoretical grid-tied and net-metered PV system and business-as-usual power from the grid. The graph shows the difference in cumulative cash flow between the PV option and the grid power option. The calculator can be run for either a financed system with a 30-year term or an upfront cash situation. The calculator takes into account energy cost averted, federal and local/state rebates, additional down payments for financed systems, interest payments for financed systems, tax benefit of mortgage interest, electricity cost inflation, potential Solar Renewable Energy Credit (SREC) income and inverter replacement cost. The loan-interest information is currently set up based on a 30-year loan, but the formulas could be re-worked for different loan terms.