Solar payback calculator

Simple and discounted payback from year-by-year cash flows. A design aid, not financial advice. Decimal commas are accepted.

System cost (USD) Upfront incentive (% of cost) Year-1 output (kWh) Degradation (% per year) Used on site (%) Import rate (USD per kWh) Export rate (USD per kWh) Import rate escalation (% per year) O&M (USD per year) Discount rate (% nominal) Horizon (years, 1 to 50)

Net cost (USD)-

Year-1 saving (USD)-

One-year formula (years)-

Simple payback (years)-

Discounted payback (years)-

NPV at discount rate (USD)-

IRR over horizon-

LCOE (USD per kWh)-

Model: year-t saving = output x (share used x import rate + exported share x export rate) - O&M. Import rate escalates from year 2; export rate stays flat. The incentive is taken off the cost at year 0. Payback is interpolated within the year it is reached. LCOE is net cost plus discounted O&M over discounted energy, before tax.