A Free Calculator · Your System, Your Rate · Updated 2026
How many years until your solar panels pay for themselves?
Solar payback isn't a single national number — it's your system size, your local
sun, your installed price, and your electricity rate. Enter those below and the
calculator returns the payback period, annual production, first-year savings, your
net cost after the federal tax credit, and 25-year net savings. Every formula is
shown, nothing is hidden, and no figure is presented as gospel.
Years to break even·Net cost after the 30% credit·25-year net savings
Read this first
This is an estimate, not financial or tax advice. Real payback depends on your
actual itemized quotes, your utility's net-metering rules, and your tax situation — the
federal solar credit is a non-refundable tax credit, so you need enough tax
liability to use it. It also depends on roof orientation and shading, and on panel
degradation (panels lose roughly 0.5% of output per year), which this simple model omits,
so it slightly overstates long-run production. Treat the sun-hours, cost-per-watt, and
price-escalation defaults as editable approximations, and always get three itemized quotes
before deciding.
Set your system size, local peak sun hours, installed cost, and electricity rate, and the results update as you go. Adjust the incentive and the annual price increase for a more precise — or more conservative — estimate.
Your system & site
kW
Typical residential systems are ~5–10 kW.
hrs/day
Average daily peak-sun-hours for your location — roughly 3 (cloudy north) to 6 (desert SW). See NREL PVWatts.
Installed price per watt before incentives — typically ~$2.50–$3.50/W (varies a lot by region and installer).
Electricity, incentives & assumptions
$/ kWh
From your bill; this is what each solar kWh offsets. U.S. average ≈ 16–17¢ — EIA.
%
The U.S. federal residential solar tax credit (ITC) is 30% of system cost through 2032, then steps down (26% in 2033, 22% in 2034) under the Inflation Reduction Act. State/local/utility incentives are extra and vary — confirm current rules at energy.gov.
%/yr
Utility rates tend to rise over time; 0% gives a flat, conservative estimate.
Solar pays for itself in
Annual production
Year-1 savings
Net cost after credit
25-year net savings
The formulas, in full
Nothing here is a black box. These are the exact calculations the tool runs — the same
arithmetic you could do on paper. The only judgment calls are the inputs you supply.
6 — Payback period (walk the years until savings cover net cost)
Accumulate cumulative_savings year by year until it reaches net_cost.
payback_years = n − (cumulative_after_n − net_cost) ÷ savings_in_year_n
When e = 0 this reduces to: payback_years = net_cost ÷ year1_savings
Capped at 80 years; if it never pays back, the tool says so.
7 — 25-year net savings
savings_25yr = Σ savings_in_year_n for n = 1 … SYSTEM_LIFETIME_YEARS
net_25yr = savings_25yr − net_cost
Production & year-1 savings by system size
A quick sense of scale: estimated annual production and first-year savings for common
residential system sizes, all computed at 4.5 peak sun hours per day, 15% system losses,
and a $0.17/kWh electricity rate. These are fixed example assumptions — use the
calculator above with your own numbers for a real estimate.
System size
Est. annual production (4.5 sun-hrs, 15% loss)
Year-1 savings (at $0.17/kWh)
Notes
5 kW
~6,981 kWh
~$1,186.71
Small home or modest usage; fits most roofs easily.
7 kW
~9,773 kWh
~$1,661.39
Common mid-size residential system (this page's default).
10 kW
~13,961 kWh
~$2,373.41
Larger home, higher usage, or planning for an EV.
13 kW
~18,150 kWh
~$3,085.44
Large household; check roof area and utility interconnection limits.
Computed as production = kW × 4.5 × 365 × 0.85 and year-1 savings = production × $0.17.
Your real production depends on your local peak sun hours, roof tilt and orientation,
shading, and equipment; your real savings depend on your electricity rate and your
utility's net-metering rules. This table omits panel degradation and price escalation —
it is a same-year snapshot only.
What actually moves your payback
Three things decide whether solar is a 7-year win or a 15-year maybe: the tax credit, how
your utility values the power you produce, and the two site inputs you should never guess
at — your sun hours and your rate.
The federal tax credit is 30% — but it's a tax credit, not a rebate
The federal residential solar credit (the ITC) is 30% of system cost through 2032, scheduled to step down to 26% in 2033 and 22% in 2034. It is non-refundable: it lowers the federal income tax you owe rather than sending you a check, so you must have enough tax liability to use it (unused amounts can generally carry forward). Tax law changes — confirm current rules and your own eligibility with a tax professional before counting on the full 30%.
Net metering decides what each kWh is worth
This calculator assumes every solar kWh you produce offsets a kWh you'd otherwise buy at your full retail rate — true under traditional full-retail net metering. Many utilities have moved to net billing, lower export credits, or time-of-use rates that credit midday solar at a low price while charging full price for the evening power you buy back. Under those policies your real value per produced kWh can be well below your retail rate, stretching the payback. Check your specific utility's current net-metering or export-credit policy before trusting any estimate.
Your sun-hours and rate move the answer more than anything
Two homes with identical hardware can have very different paybacks. A site at 6 peak sun hours produces about a third more energy than one at 4.5; a $0.30/kWh rate pays back more than twice as fast as a $0.13/kWh rate. These two inputs swing the result far more than small differences in cost per watt or assumed price escalation, so look up your real peak-sun-hours with PVWatts and pull your true blended rate off your bill rather than accepting the defaults.
How to get a trustworthy number
The calculator is exact for the inputs you give it. Tightening up the inputs — and
modeling conservatively — is what turns the estimate into something you can act on.
Get three itemized quotes
Cost per watt varies widely by installer and region. Get at least three itemized quotes (panels, inverter, labor, permitting, and any adders broken out) and use the real installed price per watt in the calculator instead of an assumed figure.
Check your utility's net-metering policy
Call your utility or read your rate schedule to find out exactly how exported solar is credited — full retail, a lower export rate, or time-of-use. This determines how much each produced kWh is really worth and can change the payback materially.
Confirm ITC eligibility with a tax pro
The 30% credit only helps if you owe enough federal tax to claim it. Confirm your eligibility, your expected liability, and the current percentage with a tax professional before assuming you'll capture the full credit in the net-cost figure.
Look up your local peak-sun-hours
Use NREL PVWatts with your address, roof tilt, and orientation for a far more accurate production estimate than the generic sun-hours default. Plug that production back in by adjusting the sun-hours figure to match.
Model conservatively
If you want a cautious estimate, set the annual price increase to 0% (flat electricity prices) and use the higher end of cost-per-watt quotes. A system that pays back acceptably under conservative assumptions is a safer bet than one that only works if prices climb.
Where to buy
Got your numbers? Here's where to pick up what you need:
The units and acronyms that show up on a solar quote, a spec sheet, or an electric bill —
in plain English.
Peak sun hours
The number of equivalent hours per day that the sun delivers full-strength radiation (1,000 watts per square meter) at your location. It is not the same as daylight hours — it bundles a whole day's varying sunlight into an equivalent count of full-power hours. Typical values run from about 3 in the cloudy north to 6 in the desert Southwest.
Derate / system losses
The combined real-world losses that keep a system from producing its nameplate output — inverter inefficiency, wiring resistance, soiling (dirt), shading, and temperature effects. Expressed as a percentage, it's converted to a production multiplier: derate = 1 − (losses% ÷ 100). PVWatts' default total loss is roughly 14%.
kW vs kWh
A kilowatt (kW) is power — the rate of energy flow, and how a solar system's size is described (a "7 kW system"). A kilowatt-hour (kWh) is energy — power sustained over time, and the unit your utility bills you in. A 7 kW system doesn't make 7 kWh; it makes 7 kW × (peak sun hours) × (derate) of energy each day.
ITC (federal solar tax credit)
The Residential Clean Energy Credit, commonly called the Investment Tax Credit. It equals 30% of eligible system cost through 2032 under the Inflation Reduction Act, scheduled to drop to 26% in 2033 and 22% in 2034. It is a non-refundable tax credit, so you need federal tax liability to use it; confirm current rules with a tax professional.
Net metering
The utility policy governing what you're credited for solar power you export to the grid. Under full-retail net metering, an exported kWh offsets a kWh you'd buy at the retail rate. Many utilities now use less generous net billing or export-credit schemes, which lower the real value of your production and lengthen payback.
Payback period
The number of years until the cumulative electricity-bill savings from a system equal its net cost (after the tax credit). With flat prices it's simply net cost ÷ year-1 savings; with rising prices each later year saves a little more, so payback comes slightly sooner.
Panel degradation
The gradual decline in a panel's output as it ages — commonly around 0.5% per year, so a panel might produce roughly 85–90% of its original output after 25 years. This simple calculator omits degradation, which means it slightly overstates production (and savings) in later years.
Frequently asked
Payback is the number of years it takes for the electricity-bill savings from a solar system to add up to its net cost (the price after the federal tax credit and any other incentives). Net cost is your gross install price times one minus your incentive percentage; annual savings is the energy your system produces in a year times your electricity rate. In the simplest case — flat prices — payback is just net cost ÷ year-1 savings. This calculator also lets you assume electricity prices rise a few percent a year, which shortens payback slightly because each later year of savings is worth more; it walks year by year, adding the growing savings until they reach the net cost, and reports the fractional year where that happens. It's a deterministic estimate from your inputs — get itemized quotes for the real figures.
The federal residential solar credit — the Residential Clean Energy Credit, often called the ITC — is 30% of the cost of an eligible home solar system through 2032 under the Inflation Reduction Act. It is scheduled to step down to 26% in 2033 and 22% in 2034 before expiring for residential systems unless extended. Critically, it is a non-refundable tax credit, not a rebate: it reduces the federal income tax you owe, so you need enough tax liability to use it (unused credit can generally carry forward). State, local, and utility incentives are separate and vary widely. Tax rules change, so confirm the current percentage and your eligibility with a tax professional. The calculator defaults the incentive to 30% but lets you change it.
Annual production is roughly your system size in kilowatts × your location's average daily peak sun hours × 365 days × a derate factor for system losses. For example, a 7 kW system at 4.5 peak sun hours per day with 15% losses produces about 7 × 4.5 × 365 × 0.85 ≈ 9,773 kWh per year. Peak sun hours aren't literal daylight hours — they're the equivalent hours of full-strength sun, typically around 3 in the cloudy north to 6 in the desert Southwest. Look up your location with NREL PVWatts for a far more precise figure that accounts for your roof tilt, orientation, and local weather. This calculator uses the simple formula above and omits panel degradation, so it slightly overstates production in later years.
It can, but the math changes. If you sell before the system has paid for itself through bill savings, what matters is how much the solar adds to your home's sale price. Studies have found buyers often pay a premium for an owned (not leased) system, but that premium varies by market, system age, and whether the panels are paid off. A leased system or one with an outstanding loan can complicate a sale and may need to be transferred or paid off at closing. If you expect to move within a few years, weigh the likely resale premium against the unrecovered net cost rather than assuming you'll capture the full multi-decade savings shown here. This calculator models the long-run, stay-put case; it doesn't estimate resale value.
Net metering is the utility policy that decides what each solar kWh is actually worth. Under full retail net metering, every kWh your panels send to the grid offsets a kWh you'd otherwise buy at the full retail rate — so a kWh produced equals a kWh saved, which is the assumption baked into this calculator. But many utilities have moved to less generous arrangements: net billing, lower export credits, or time-of-use rates where midday solar is credited at a low price while the evening power you buy back is expensive. Under those rules your real savings per produced kWh can be well below your retail rate, lengthening payback. Always check your specific utility's current net-metering or export-credit policy before trusting any payback estimate — it moves the answer as much as your rate does.
This calculator models a cash purchase — you pay the net cost up front and the system pays you back in bill savings. We deliberately leave out loans, leases, and power-purchase agreements because financing terms are a your-money-your-life decision that turns on your specific interest rate, loan length, dealer fees, and how those costs interact with the tax credit. A loan can change a system from cash-flow-positive on day one to net-negative for years, depending on the rate, and the wrong assumption here would be worse than no number at all. Get itemized financing quotes and compare the all-in financed cost against the cash payback this tool estimates, ideally with help from a financial professional. We'd rather show you the clean cash baseline than bury a guess about your loan terms in the math.
Common mistakes with this calculator
Solar payback math has four common pitfalls that can shift the estimate by years.
Confusing daylight hours with peak sun hours
Peak sun hours are not the same as hours of daylight. They represent the equivalent number of hours per day at full 1,000 W/m² irradiance — a way of expressing total daily solar energy in consistent units. A location with 10 hours of daylight might receive only 4–5 peak sun hours depending on cloud cover, angle, and season. Use NREL's PVWatts tool or a local solar irradiance map to find the peak sun hours for your specific location, not just how long the sun is up. Source: NREL PVWatts.
Treating the federal tax credit as a cash rebate
The residential clean energy credit (currently 30%) reduces what you owe in federal income tax — it is not a refund check and it is not refundable. If your total tax liability for the year is less than the credit amount, you only capture the portion you owe; the remainder carries forward to future years. If you have little or no federal tax liability, the effective value of the credit is much lower than 30% of system cost. Source: US DOE IRS Form 5695 guidance.
Assuming full retail net metering
Not all utilities compensate exported solar power at the full retail rate. Some pay a wholesale or avoided-cost rate — often half or less of what you pay to buy power. California's NEM 3.0, for example, dramatically reduced export rates versus earlier programs. Enter the rate your utility actually pays for exported kWh, not what you pay on your bill, or your savings estimate will be higher than reality.
Ignoring panel degradation
Solar panels lose output slowly over time — typically around 0.5% per year for quality panels, meaning a system produces roughly 87% of its original output at year 25. This calculator uses a flat annual production figure; the real payback period is slightly longer than shown because output (and therefore savings) declines each year. Over a 25-year span, the cumulative effect is meaningful.