Estimate net cost, payback period and long-run savings from your bill savings and any incentives.
This calculator answers a simple question: how long until the electricity you no longer buy has paid for the system? Enter the system cost before incentives, the total incentives or rebates you expect to receive, the savings on your electric bill in the first year, how fast you expect electricity prices to rise, and how many years you want to look ahead.
Formula: net cost = cost - incentives. Each year's savings equal the previous year's savings x (1 + yearly increase). Payback is the point where cumulative savings reach the net cost.
Worked example (illustrative): a $24,000 system with no incentives and $1,800 of first-year savings growing 3% a year saves about $1,800, $1,854, $1,910 and so on. Cumulative savings pass $24,000 around year 11 to 12.
Limits: the tool ignores panel degradation, inverter replacement, financing interest, maintenance and changes to net metering rules, all of which can lengthen payback. Treat the default inputs as examples and replace them with the production estimate and rate data from your own proposal and utility bill.
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