The Solar Index name belongs to this domain's legacy editorial record. The current site does not reproduce or validate a historical parcel model, its input data, geographic coverage, output accuracy, or past performance.
What the current sizing and cash-flow tool does
The Solar Savings Calculator calculates target system size only from documented annual household use, a chosen coverage target, and address- and roof-specific annual production per installed kilowatt. It calculates first-year electricity benefit only from entered utility costs, applicable export credits, and owner costs. The same-scope cash price and each source-event date must also be entered before a result appears.
What it does not do
The tool does not accept a state-rate query parameter, infer household values from a monthly bill or rough location, supply national price or production defaults, calculate a tax credit, or infer payback. Payback belongs in the explicit year-by-year owner ledger, which reports a first whole-year crossover rather than a fractional result.
Where address-specific evidence comes from
Use a documented site study or the free NREL PVWatts tool for address- and roof-specific production evidence, then retain the source event and date. The methodology page publishes the exact sizing and first-year cash-flow formulas used here.