Energy
Estimate simple payback from system cost and annual energy savings.
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Solar payback calculator guide
Simple payback answers the first question anyone asks about a solar quote: how many years until the savings have covered what I paid? This calculator subtracts any incentives — a tax credit, a state or utility rebate, a net-metering sign-up bonus — from the installed system cost, then divides by the annual savings on your electricity bill. Annual savings are normally the kilowatt-hours the array will produce (from the solar-generation calculator) multiplied by the tariff you avoid, plus any export income; take care to use the price you would actually have paid, including tiered or peak rates. The result is a planning number for comparing quotes and for deciding whether a battery or a larger array is worth it. It ignores financing interest, inflation of electricity prices, panel degradation of about 0.5 percent a year, inverter replacement after 10 to 15 years, maintenance, insurance, and any change in the value of your home. Loan payments and taxes on export income are also excluded, so treat the figure as a lower bound if you are borrowing.
Net system cost = system cost − incentives. Simple payback (years) = net system cost ÷ annual savings. Lifetime return (not shown) ≈ annual savings × system life − net cost.
Worked example with the defaults: an installed system cost of $18,000, annual savings of $1,800, and no incentive. Net cost = $18,000 − $0 = $18,000. Payback = $18,000 ÷ $1,800 = 10 years, the figure the calculator displays. If a 30 percent tax credit applied, the net cost would be $18,000 − $5,400 = $12,600 and payback would fall to $12,600 ÷ $1,800 = 7 years. If electricity prices rose so savings averaged $2,200 a year, payback on the full price would be about 8.2 years.
System cost and incentives are in currency, entered as totals (not per watt). To convert a per-watt quote, multiply by system size in watts: $3.00/W × 5,000 W = $15,000. Annual savings are currency per year; estimate them as annual kWh generated × your tariff per kWh, adjusted for the share you export at a lower feed-in rate. Payback is in years to one decimal; multiply the fraction by 12 for months, so 10.5 years is 10 years 6 months.
This is a modelled estimate, not a meter reading. Real consumption moves with weather, occupancy, appliance age, standing charges, and tariff structure, and equipment rarely runs at its nameplate rating. Use the figure to compare options against each other, then confirm against your own bill and the manufacturer's specification before committing to a purchase. On this page the figure rests entirely on system cost, annual savings, incentives, market / jurisdiction, effective date, data source, update owner and review date, so start there if the solar payback calculator returns something you did not expect.
Good to know: multiplying annual generation by the full import tariff assumes you use every kWh at home, which is wrong for a household that is out all day with no battery — half or more may be exported at a credit worth a third of the import price. Entering the pre-incentive cost with post-incentive savings, or vice versa, is another common inconsistency. Simple payback also treats a system that pays back in 10 years and then dies the same as one that lasts 25; compare quotes on lifetime savings too, and remember an inverter replacement of $1,000 to $2,500 will likely land inside the payback period.
Energy results depend on tariffs, equipment behavior, region, weather, and installation assumptions. Verify rates and electrical decisions with the utility, manufacturer, or qualified professional.
Sources
How it works
Estimate simple payback from system cost and annual energy savings. This tool explains the calculation so you can adjust the assumptions to match your situation.
Worked example
With System cost = 18000 $ · Annual savings = 1800 $/year · Incentives = 0 $ → 10 years (simple payback period). Change an input above and this example updates with your numbers.
Common questions
Typically 6 to 12 years for a residential system. An $18,000 system saving $1,800 a year pays back in 10 years with no incentive, or 7 years with a 30 percent credit. High tariffs, good sun, and daytime self-consumption shorten the period; low export credits lengthen it.
Often yes, because panels are warranted for 25 years and can produce for 30. A 10-year payback on a 25-year system means roughly 15 years of largely free electricity, though you should budget for one inverter replacement and expect output to decline about 0.5 percent per year.
Estimate annual kWh from the solar-generation calculator, split it into kWh you use at home and kWh you export, then value each at its own rate. For example, 6,570 kWh with 60 percent self-used at $0.16 and 40 percent exported at $0.05 is $631 + $131 = $762, not $1,051.
With rooftop systems costing roughly $600 to $900 per kW and tariffs of $0.06 to $0.10 per kWh, a 5 kW array yielding about 6,500 to 7,500 kWh a year saves $450 to $750, giving 5 to 9 years before subsidies. India’s PM Surya Ghar subsidy can cut a 3 kW system’s payback to 3 to 5 years.
No. This calculator ignores financing, inflation, degradation, and maintenance. If you finance the system, add total interest to the cost or compare the loan payment with the monthly saving instead; a $15,000 loan at 7 percent over 10 years adds roughly $5,900 in interest.