How does the solar payback period & ROI calculator work?
The calculator prices your system, subtracts every incentive you qualify for, then projects 25 years of bill savings against rising utility rates, declining panel output, and real maintenance costs — reporting the year you break even and what the investment returns after that.
Pick your state
Your state's current EIA electricity rate, sun hours, installed cost, export policy, and incentive load automatically.
Enter your system & quote
Set system size and the cost per watt from your quote, then adjust incentives to what you actually qualify for.
Read payback, ROI & IRR
See your break-even year, 25-year return, annualized IRR, and the full year-by-year cash flow.
How solar payback works
Solar payback is a break-even calculation, not a savings estimate. You spend a large amount once, then recover it in small annual increments made of electricity you no longer buy. The break-even year is where those increments finally add up to what you spent. What makes it harder than dividing cost by first-year savings is that all three of the moving parts change every year: the value of a kWh goes up, the number of kWh goes down, and the system occasionally costs you money. Getting payback right means modeling all three.
1. How your utility credits the energy — net metering vs. net billing
A rooftop array does two different things, and they are not worth the same amount. Energy you use the moment it's produced simply doesn't get bought from the utility, so it's worth your full retail rate. Energy you produce but don't use gets exported to the grid, and what that's worth depends entirely on your state's policy.
Under full-retail net metering, your meter effectively runs backwards: an exported kWh earns the same credit as a kWh you later consume. Production and consumption net out over the billing period, so the split between self-consumed and exported energy makes no difference to your savings. Most states still work this way.
Under net billing, exports are credited at an avoided-cost or export-tariff rate below retail — anywhere from about 15% of retail in California to roughly two-thirds in Nevada, as the table below shows. California's NEM 3.0 is the best-known example, and Hawaii, Arizona, Nevada, Utah, Indiana, and Michigan all use variations. In those states, the share of your production you actually consume on site becomes the largest single lever on payback, which is why batteries shorten payback meaningfully in California and barely register in a full-net-metering state. It is also why the slowest-payback states further down this page are not simply the cloudy ones — Indiana and Michigan land there on export credits, not weather.
| State | Retail rate | Export credit | Export earns | Policy |
|---|---|---|---|---|
| Arizona | 15.23¢ | 7.5¢ | 49% of retail | Net billing — exports credited at a utility export rate below retail |
| California | 33.25¢ | 5.0¢ | 15% of retail | NEM 3.0 net billing — exports credited at avoided cost, far below retail |
| Hawaii | 52.00¢ | 10.0¢ | 19% of retail | No net metering for new systems — Smart Export / CGS+ export credits |
| Indiana | 18.15¢ | 4.5¢ | 25% of retail | Excess generation credited near wholesale, not retail |
| Michigan | 22.01¢ | 6.5¢ | 30% of retail | Distributed generation tariff — outflow credited below retail |
| Nevada | 13.60¢ | 9.0¢ | 66% of retail | Tiered net billing — exports credited at a percentage of retail |
| Texas | 16.44¢ | 8.0¢ | 49% of retail | No statewide mandate — buyback depends on your retail provider |
| Utah | 12.96¢ | 5.0¢ | 39% of retail | Export credit program well below retail |
Every state not listed above is modeled at full-retail net metering, where the export rate matches your retail rate. Set your own self-consumption share and export credit in the advanced section if your utility's tariff differs — 30–40% self-consumption is typical without a battery, 60–80% with one.
2. Degradation — the array makes less every year
Solar panels lose a small amount of output annually as the cells age. Modern crystalline-silicon modules degrade at roughly 0.5% a year, which sounds trivial until you compound it: by year 25 the array is producing about 88% of its first-year output. Manufacturer performance warranties are written around this curve, typically guaranteeing 80–87% of nameplate output at year 25. The calculator applies your degradation rate to every projected year rather than assuming flat production, because ignoring it overstates lifetime savings by several thousand dollars on a typical system.
3. Inflation — the energy gets more valuable every year
Working in the opposite direction, and more powerfully, is the rising price of grid electricity. Residential rates have climbed a few percent a year on average, and the kWh your system produces in year 20 offsets year-20 prices, not today's. This is why rate escalation matters so much to payback: at 3% a year, a kWh worth 18 cents today is worth about 33 cents in year 21, so the second half of the system's life is worth far more than the first. Degradation and escalation pull against each other, and at typical values escalation wins comfortably — annual savings rise over time despite the array slowly weakening.
Set escalation to 0% if you want a deliberately pessimistic floor on payback. That single change typically adds two to four years to the break-even date, and it's a useful sanity check on any quote whose savings projection assumes aggressive rate increases.
Net cost = (kW × 1,000 × $/W) − federal credit − state and utility incentives. Each year's production = system size × peak sun hours × 365 × performance ratio × (1 − degradation)^(year−1). Each year's savings = production × (self-consumed share × retail rate + exported share × export rate), with both rates escalated forward. Net cash flow subtracts annual O&M and any inverter replacement. ROI = total net profit ÷ net cost. IRR is the discount rate at which the full 25-year cash-flow series nets to zero.
Average payback period by state
The table below runs the same 8 kW system through this calculator for every state, using that state's own electricity rate, peak sun hours, installed cost, export policy, and statewide incentive, with the calculator's default assumptions (3% rate escalation, 0.5% annual degradation, 40% self-consumption, $150/yr maintenance, and a $2,000 inverter replacement in year 13). Select your state in the calculator above and the numbers will match exactly.
Payback ranges from 5.8 years in Hawaii to 22.1 years in Indiana, with a median around 11.5 years. The fastest five are Hawaii (5.8), New York (6.1), Connecticut (8.3), New Mexico (8.3), Rhode Island (8.3). The slowest five are Indiana (22.1), Michigan (19.4), Utah (18.6), Washington (17.4), North Dakota (15.9). Notice that sunshine alone doesn't decide it — Hawaii and New York sit at the top on high electricity rates, while sun-rich states with cheap power sit well down the list.
| State | Electricity rate | Sun hours | Installed cost | Net cost | Year 1 savings | Payback | 25-yr ROI |
|---|---|---|---|---|---|---|---|
| Alabama | 16.77¢/kWh | 4.6 | $2.60/W | $20,800 | $1,734 | 11.4 yrs | 157% |
| Alaska | 28.23¢/kWh | 3.0 | $3.30/W | $26,400 | $1,904 | 13.6 yrs | 124% |
| Arizona | 15.23¢/kWh | 6.4 | $2.24/W | $16,920 | $1,524 | 10.8 yrs | 173% |
| Arkansas | 14.36¢/kWh | 4.6 | $2.55/W | $20,400 | $1,485 | 14.0 yrs | 120% |
| California | 33.25¢/kWh | 5.5 | $2.53/W | $20,240 | $2,016 | 9.7 yrs | 211% |
| Colorado | 16.16¢/kWh | 5.4 | $2.60/W | $20,800 | $1,962 | 10.1 yrs | 194% |
| Connecticut | 27.37¢/kWh | 4.2 | $2.77/W | $22,160 | $2,585 | 8.3 yrs | 272% |
| Delaware | 19.38¢/kWh | 4.4 | $2.75/W | $22,000 | $1,917 | 10.9 yrs | 171% |
| District of Columbia | 25.40¢/kWh | 4.4 | $2.90/W | $23,200 | $2,513 | 8.8 yrs | 244% |
| Florida | 15.17¢/kWh | 5.2 | $2.45/W | $19,600 | $1,774 | 10.6 yrs | 179% |
| Georgia | 15.84¢/kWh | 4.8 | $2.50/W | $20,000 | $1,710 | 11.2 yrs | 163% |
| Hawaii | 52.00¢/kWh | 5.8 | $3.20/W | $20,600 | $3,495 | 5.8 yrs | 450% |
| Idaho | 12.35¢/kWh | 4.9 | $2.45/W | $19,600 | $1,361 | 14.7 yrs | 107% |
| Illinois | 23.85¢/kWh | 4.3 | $2.85/W | $22,800 | $2,306 | 9.4 yrs | 220% |
| Indiana | 18.15¢/kWh | 4.2 | $2.75/W | $22,000 | $941 | 22.1 yrs | 20% |
| Iowa | 14.14¢/kWh | 4.4 | $2.70/W | $21,600 | $1,399 | 15.4 yrs | 94% |
| Kansas | 15.13¢/kWh | 5.0 | $2.55/W | $20,400 | $1,701 | 11.4 yrs | 156% |
| Kentucky | 14.98¢/kWh | 4.3 | $2.65/W | $21,200 | $1,448 | 14.7 yrs | 106% |
| Louisiana | 14.15¢/kWh | 4.7 | $2.60/W | $20,800 | $1,495 | 14.1 yrs | 117% |
| Maine | 28.63¢/kWh | 4.2 | $2.95/W | $23,600 | $2,704 | 8.4 yrs | 266% |
| Maryland | 21.77¢/kWh | 4.4 | $2.75/W | $21,000 | $2,154 | 9.4 yrs | 222% |
| Massachusetts | 28.82¢/kWh | 4.3 | $3.35/W | $25,800 | $2,786 | 8.8 yrs | 246% |
| Michigan | 22.01¢/kWh | 4.0 | $2.90/W | $23,200 | $1,143 | 19.4 yrs | 43% |
| Minnesota | 16.95¢/kWh | 4.3 | $2.85/W | $22,800 | $1,639 | 13.9 yrs | 120% |
| Mississippi | 16.16¢/kWh | 4.7 | $2.60/W | $20,800 | $1,708 | 11.6 yrs | 152% |
| Missouri | 13.68¢/kWh | 4.5 | $2.60/W | $20,800 | $1,384 | 15.1 yrs | 99% |
| Montana | 14.67¢/kWh | 4.6 | $2.75/W | $22,000 | $1,517 | 14.5 yrs | 109% |
| Nebraska | 13.59¢/kWh | 4.8 | $2.65/W | $21,200 | $1,467 | 14.6 yrs | 109% |
| Nevada | 13.60¢/kWh | 6.2 | $2.35/W | $18,800 | $1,511 | 11.9 yrs | 143% |
| New Hampshire | 27.33¢/kWh | 4.2 | $3.05/W | $24,400 | $2,581 | 9.0 yrs | 237% |
| New Jersey | 23.27¢/kWh | 4.4 | $2.85/W | $22,800 | $2,302 | 9.5 yrs | 219% |
| New Mexico | 14.12¢/kWh | 6.4 | $2.40/W | $17,280 | $2,032 | 8.3 yrs | 268% |
| New York | 29.93¢/kWh | 4.1 | $2.75/W | $17,000 | $2,759 | 6.1 yrs | 419% |
| North Carolina | 15.09¢/kWh | 4.7 | $2.45/W | $19,600 | $1,595 | 11.7 yrs | 148% |
| North Dakota | 13.61¢/kWh | 4.5 | $2.75/W | $22,000 | $1,377 | 15.9 yrs | 87% |
| Ohio | 19.52¢/kWh | 4.1 | $2.75/W | $22,000 | $1,799 | 11.5 yrs | 153% |
| Oklahoma | 13.38¢/kWh | 5.1 | $2.45/W | $19,600 | $1,534 | 13.2 yrs | 138% |
| Oregon | 16.27¢/kWh | 4.0 | $2.80/W | $22,400 | $1,463 | 15.2 yrs | 97% |
| Pennsylvania | 21.55¢/kWh | 4.2 | $2.65/W | $21,200 | $2,035 | 10.0 yrs | 200% |
| Rhode Island | 29.46¢/kWh | 4.3 | $3.10/W | $24,800 | $2,848 | 8.3 yrs | 268% |
| South Carolina | 16.18¢/kWh | 4.8 | $2.50/W | $16,500 | $1,746 | 9.2 yrs | 226% |
| South Dakota | 15.73¢/kWh | 4.7 | $2.70/W | $21,600 | $1,662 | 13.2 yrs | 136% |
| Tennessee | 14.47¢/kWh | 4.4 | $2.55/W | $20,400 | $1,432 | 14.5 yrs | 111% |
| Texas | 16.44¢/kWh | 5.1 | $2.18/W | $17,440 | $1,304 | 14.0 yrs | 122% |
| Utah | 12.96¢/kWh | 5.5 | $2.35/W | $18,800 | $1,012 | 18.6 yrs | 53% |
| Vermont | 24.89¢/kWh | 4.1 | $3.00/W | $24,000 | $2,294 | 9.9 yrs | 202% |
| Virginia | 17.61¢/kWh | 4.5 | $2.60/W | $20,800 | $1,782 | 11.1 yrs | 164% |
| Washington | 14.95¢/kWh | 3.7 | $2.75/W | $22,000 | $1,244 | 17.4 yrs | 67% |
| West Virginia | 16.80¢/kWh | 4.1 | $2.70/W | $21,600 | $1,549 | 14.1 yrs | 118% |
| Wisconsin | 19.74¢/kWh | 4.2 | $2.95/W | $23,600 | $1,864 | 11.9 yrs | 145% |
| Wyoming | 14.80¢/kWh | 5.3 | $2.60/W | $20,800 | $1,764 | 11.2 yrs | 161% |
These are statewide averages, and the spread inside a single state can be as wide as the spread between states — a customer of a high-rate investor-owned utility and a customer of a low-rate municipal or co-op utility a county apart will get very different results. Treat the table as a starting point, then replace the rate with the effective rate from your own bill. The U.S. average residential rate for the same period was 18.44¢/kWh.
Sources: U.S. Energy Information Administration, Electric Power Monthly Table 5.6.A (May 2026); state-average installed cost benchmarks from residential market reporting; incentive programs verified against DSIRE. Table last reviewed August 2026.
Federal vs. state incentives in 2026
2026 is the first year in nearly two decades in which a homeowner buying a solar system outright receives nothing from the federal government. That single change reshaped the payback math nationwide, and it moved the decision almost entirely onto state and utility programs. Here is what each layer of incentive is actually worth now:
| Incentive | 2026 status | Typical value | Who claims it |
|---|---|---|---|
| Federal residential credit (Section 25D) | Expired after Dec 31, 2025 | 0% | No longer available |
| Federal commercial credit (Section 48E) | Active | 30%+ of cost | The system owner — reaches homeowners only via a lease or PPA |
| State income tax credits | Active in 7 states | 10–35% of cost, usually capped | You, on your state return |
| State & utility rebates | Varies widely | Flat sum or per-watt | Often assigned to the installer and netted off your price |
| SREC / performance payments | Active in ~6 markets | Paid per MWh produced, over a fixed term | You, as income rather than a cost reduction |
| Property & sales tax exemptions | Common | Removes tax on the added home value or purchase | Automatic where offered |
What happened to the federal credit
The 30% residential Clean Energy Credit (Section 25D) expired for systems placed in service after December 31, 2025 under the One Big Beautiful Bill Act. For a homeowner buying a system today the federal contribution is zero, which is why that field defaults to 0% here — a calculator still applying 30% will understate your payback by roughly three to five years. Two paths to federal value remain. If your system was placed in service on or before December 31, 2025, you can still claim the credit on that year's return. And under a lease or power purchase agreement, the system's owner claims the Section 48E commercial credit and reflects it in your monthly payment — though you give up ownership of the savings, and of any resale premium, in exchange.
State credits and rebates that still apply
With the federal credit gone, state and local programs now decide whether a project pencils. 7 states still offer a statewide residential credit or rebate:
| State | Program | Value | Worth on the benchmark system |
|---|---|---|---|
| Arizona | Arizona Residential Solar Energy Credit | 25% of cost, capped at $1,000 | $1,000 |
| Hawaii | Renewable Energy Technologies Income Tax Credit | 35% of cost, capped at $5,000 | $5,000 |
| Maryland | Residential Clean Energy Rebate Program | $1,000 rebate | $1,000 |
| Massachusetts | Residential Renewable Energy Income Tax Credit | 15% of cost, capped at $1,000 | $1,000 |
| New Mexico | New Solar Market Development Income Tax Credit | 10% of cost, capped at $6,000 | $1,920 |
| New York | Solar Energy System Equipment Credit | 25% of cost, capped at $5,000 | $5,000 |
| South Carolina | Solar Energy Tax Credit (10-yr carryforward) | 25% of cost, capped at $3,500 | $3,500 |
Beyond these, several states pay for production rather than installation: Illinois Shines, New Jersey's SuSI program, the Massachusetts SMART program, and SREC markets in Maryland, Pennsylvania, and Washington D.C. all pay per megawatt-hour generated over a fixed term. Those payments are income rather than a cost reduction, so model them by raising your effective electricity rate rather than entering them in the incentive field. Utility and municipal rebates — Austin Energy in Texas, various co-op programs, and city-level offsets — are not captured in the state table; look yours up at DSIRE and add it to the state and utility incentive field.
One caution on tax credits specifically: a nonrefundable credit is only worth what your tax liability can absorb. South Carolina's 25% credit is capped at $3,500 a year with a 10-year carryforward, so a large system delivers its value over several returns rather than all at once. If your state liability is small, the credit may be worth less to you than the headline percentage suggests — worth confirming with a tax professional before it goes into your payback math.
What affects your ROI?
Two neighbors on the same street, the same utility, and the same rate can see paybacks years apart. Beyond the state-level variables in the table above, these are the property- and equipment-level factors that move the number most.
Roof condition and remaining life
This is the most commonly ignored line item and one of the most expensive. Panels last 25-plus years; asphalt shingles often don't. If your roof has less than about 10 years left, you will likely pay to have the array removed and reinstalled partway through its life — commonly $2,000 to $6,000 for a typical residential system, and occasionally more for complex roofs. Re-roofing first costs more upfront but avoids that charge entirely and is nearly always the better financial decision. Roof material matters too: standing-seam metal is the cheapest and least invasive to mount on, while tile and slate carry meaningful labor premiums that show up directly in your cost per watt. Model a planned re-roof by adding it to the inverter replacement field, or by raising your cost per watt.
Shading
Shade hurts more than its share of the roof suggests, because on a traditional string inverter the panels are wired in series — a single shaded module can pull down the output of every panel on its string, the way one weak link limits a chain. A chimney, vent stack, or neighbor's tree shading a corner of the array for two hours a day can cost far more than 8% of production. Microinverters and DC optimizers largely solve this by letting each panel produce independently, which is why they are standard on complex or partly shaded roofs — at a modest cost premium that usually pays for itself when shade is real. Ask any installer for a shade report with a modeled solar access percentage; if it comes back below about 85%, reflect it here by lowering peak sun hours or the performance ratio.
Panel type and efficiency
Panel efficiency matters less for ROI than most buyers assume, because you are buying a system size in kilowatts, not a panel count. A 400 W panel and a 450 W panel of the same total array size produce roughly the same energy; the higher-efficiency module just does it in less roof area. Efficiency only drives ROI when roof space is the binding constraint — a small or awkward roof where premium panels are the only way to reach the system size you need. Where panel choice does affect returns is durability and warranty: a lower degradation rate (0.25–0.4%/yr on premium modules versus 0.5–0.7% on budget ones) compounds across 25 years, and a 25-year product warranty against a 12-year one changes who pays for a mid-life failure. Enter the specific degradation rate from your quoted panel's datasheet in the advanced section.
South-facing at roughly 30° is the U.S. benchmark. East or west typically gives up 15–20% of annual output; north-facing is rarely worth wiring.
String inverters cost less but usually need replacing at 10–15 years. Microinverters cost more upfront and often carry 25-year warranties.
Oversizing past your consumption pushes production into exports, which in a net-billing state earns a fraction of retail and lengthens payback.
The widest controllable variable. Quotes for the same system routinely differ 30%+, and cost per watt feeds straight into payback.
A cash purchase is what this page models. Loan interest and dealer fees add real cost — run the loan separately and treat this as the cash case.
Time-of-use plans, tiered pricing, and fixed monthly charges all change what a kWh of solar is actually worth against a flat-rate estimate.
Worked example: a high-rate state with no incentive
8 kW in California — $2.53/W, 33.25¢/kWh, NEM 3.0 export at 5¢
A California homeowner installs an 8 kW system at the state-average $2.53 per watt. There is no federal credit in 2026 and no statewide California credit, so the full cost stands. The state averages 5.5 peak sun hours, and under NEM 3.0 exports earn about 5 cents against a 33.25-cent retail rate, so self-consumption matters — assume 40% without a battery.
- Gross and net cost: 8,000 W × $2.53 = $20,240, with no incentives to subtract.
- Year 1 production: 8 kW × 5.5 h × 365 × 0.77 ≈ 12,366 kWh.
- Year 1 savings: 40% self-consumed at $0.3325 (≈ $1,645) + 60% exported at $0.05 (≈ $371) ≈ $2,016.
- Less O&M: $150/yr, plus a $2,000 inverter replacement in year 13.
Projected forward with 3% rate escalation and 0.5% annual degradation, cumulative net cash flow covers the $20,240 cost partway through year 10.
Result: a 9.7-year payback, about 210% ROI over 25 years, and a 10.0% IRR — driven entirely by California's retail rate, since exports are worth roughly a sixth of it.
Worked example: a lower-rate state with a 25% credit
8 kW in South Carolina — $2.50/W, 16.18¢/kWh, 25% state credit
The same 8 kW system in South Carolina costs $2.50 per watt, and the state's Solar Energy Tax Credit covers 25% of cost up to $3,500 claimable per year. The retail rate is less than half California's, but full-retail net metering means every kWh is worth the same whether it's used or exported.
- Gross cost: 8,000 W × $2.50 = $20,000.
- State credit: 25% of $20,000 = $5,000, capped at $3,500 in the first year. Net cost ≈ $16,500.
- Year 1 production: 8 kW × 4.8 h × 365 × 0.77 ≈ 10,792 kWh.
- Year 1 savings: 10,792 kWh × $0.1618 ≈ $1,746, since exports earn full retail.
Result: a 9.2-year payback, about 226% ROI, and a 10.6% IRR — South Carolina's rate is half California's, but full-retail net metering and the state credit more than close the gap. The $1,500 of credit above the annual cap carries forward to year two, shortening payback further than modeled here.
Understanding each result
Payback period is the year your cumulative cash flow, net of maintenance, first covers your net system cost. It is the answer to "when do the panels pay for themselves," and it is the figure most sensitive to your electricity rate.
25-year ROI is total net profit divided by net cost. A 150% ROI means you ended the 25 years with two and a half times what you put in. It ignores timing, which is why IRR sits beside it.
Annual return (IRR) converts the whole cash-flow stream into one annualized percentage you can compare against a savings account, a bond, or an index fund. Because bill savings aren't taxed as income, the equivalent pre-tax return is meaningfully higher than the number shown.
Net cost after incentives is what you actually finance or pay out of pocket, and it is the denominator for both return figures.
Levelized cost of energy divides your lifetime cost by lifetime production for a single cents-per-kWh price you can hold directly against your utility rate.
Common ways to use this calculator
Compare your state's LCOE against your current rate before you talk to any installer.
Enter the installer's exact cost per watt and promised incentives to see the payback their proposal really implies.
Use the IRR figure to weigh a cash purchase against leaving the money invested elsewhere.
In a net-billing state, raise self-consumption from 40% to 70% and see how much payback shortens.
Limitations to keep in mind
This model uses a single flat retail rate rather than time-of-use periods, seasonal rates, or tiered pricing, and it escalates the export credit at the same rate as retail even though avoided-cost rates often move independently. It does not model financing interest — for a loan-funded system, run the payment through our solar loan calculator and treat this page's figures as the cash-purchase case. It also excludes any resale value the system adds to your home, and it assumes you have enough tax liability to use any credit you enter.
Privacy and appropriate use
Your inputs are processed directly in your browser and are not sent to a database. This is a planning-stage financial estimate, not tax, investment, or engineering advice — confirm incentive eligibility with a tax professional and get a formal site assessment from a licensed installer before committing.