Last reviewed 04 October 2026
Most published solar payback figures originate with installers, and almost all still assume a 30% federal tax credit that no longer exists. The figures here do not. Set out below are every input, every assumption and every omission, so that the arithmetic can be checked or disputed.
Simple payback divides the cost of the system by its first-year saving. It is the figure most sites publish because it is easily calculated, and it is pessimistic: it assumes electricity prices never rise.
payback = net cost ÷ first-year saving
Payback with rate rises runs the arithmetic year by year. Production falls slightly as panels age, electricity gets dearer, upkeep is deducted, and the inverter is replaced. The break-even year is the first one where the running total of savings passes the net cost. It usually lands 1–3 years earlier than simple payback, and is the figure given prominence here.
for each year n:
production = annual kWh × (1 − 0.005)^(n−1)
rate = retail rate × (1 + 0.03)^(n−1)
saving = production × 0.65 × rate
+ production × 0.35 × export rate
+ SREC income
− $150 upkeep
− $1,800 if n = 12
break-even = first year where the running total ≥ net cost
Net cost is the installed price minus any state rebate, state tax credit and federal credit — the last of which is zero in 2026.
| Input | Value used | Source | Refreshed |
|---|---|---|---|
| Annual production | 6 kW array, south-facing, 20° tilt | NREL PVWatts v8 | Yearly |
| Electricity rate | State average residential price | EIA API v2, retail sales | Monthly |
| Export credit | Full retail, a fraction of it, or 5¢ | State net metering rules via DSIRE | Quarterly |
| Installed cost | $2.85 per watt before incentives | EnergySage / SEIA market data | Quarterly |
| State incentives | Rebates, state tax credits, SREC prices | DSIRE, checked by hand | Quarterly |
| Federal tax credit | 0% | IRC Section 25D | On any law change |
Run once per state at the largest metro's coordinates, using NSRDB typical-year weather. PVWatts is the model NREL's own public calculator uses, so the figure here can be reproduced by entering the same coordinates.
A state average rather than a specific utility's rate. In states served by several utilities this is the single largest source of error on this site; an actual bill is always more accurate.
Full retail in 23 states, 40% of retail in 13, 25% in 13, and a flat 5¢ in California under NEM 3.0.
A national median. Northeastern labor and permitting run $0.30–$0.50 a watt above it; competitive Sun Belt markets run below.
Only programs open to a typical owner-occupier are counted. Utility-specific and income-qualified programs are excluded, because they do not apply state-wide.
The 30% residential credit expired on 31 December 2025 under the One Big Beautiful Bill Act. Every figure on this site assumes zero. If it returns, one setting changes and all 50 states update the same day.
These are judgments rather than measurements. Each can be varied using the controls on the map.
| Assumption | Value |
|---|---|
| Share used at home | 65% |
| Panel degradation | 0.5% a year |
| Electricity rate rises | 3% a year |
| Upkeep | $150 a year |
| Inverter replacement | $1,800 in year 12 |
| Horizon | 30 years |
The weakest assumption on the site. A household absent during the day and without storage self-uses closer to 35%. Where export credit is poor — California, Texas, the South — that difference can move payback by several years. The controls on the map allow the figure to be varied.
Standard warranty-level assumption; most tier-1 panels do slightly better.
Deliberately conservative. Several regions have run well above this recently, which would shorten every payback shown here.
Cleaning, monitoring and insurance uplift.
The reason the savings curve dips mid-chart. Most string inverters are warranted 10–12 years.
A state shown as never breaking even means the system does not repay its cost within 30 years on these settings, not that solar cannot work there.
A payback figure that includes favorable factors and omits unfavorable ones is marketing. Listed below are the omissions, and the direction in which each moves the real result.
A dealer fee on a solar loan can add 25% to the amount financed. Every figure here assumes a cash purchase; a financed system has a longer real payback than the figure shown.
Owned systems tend to lift sale price, but the premium varies far too much by market to put in a national model. Treat it as possible upside, not as part of the payback.
Under a lease the installer owns the system and claims the commercial credit, so payback does not apply; the comparison is a monthly payment against a monthly bill.
Storage changes both the cost and the self-use share. It is not in these numbers.
Where a roof requires replacement within five years, that cost and the removal-and-refit charge should be added before any comparison.
SREC income may be taxable depending on individual circumstances. It is shown gross here.
For a household on its state's average rate, with an unshaded south-facing roof and no financing, the break-even year should fall within about 18 months of the figure shown. Outside those conditions — shading, a utility well above or below the state average, a loan carrying a large dealer fee, or a self-consumption share far from 65% — the divergence widens quickly, and predominantly in one direction: real paybacks are longer more often than they are shorter. Three written quotations are more reliable than this model for any individual property.
Every source is public and free of charge:
Any figure here may be wrong. Reports identifying the state and the figure concerned are rechecked against the source.
Corrections are welcome. Identify the state and the figure concerned and send them to corrections@energycostmap.com. A figure is changed only once it has been confirmed against a primary source, and the change is recorded in the log below.
The complete dataset behind every page on this site is published as a single JSON file: states.json. It carries, for each of the 50 states, the annual generation from PVWatts, the retail rate from the EIA, the export factor and netting period taken from the serving utility's tariff, the installed cost, every incentive applied, both payback figures, the 25-year net return, and the source URL and date against which the export terms were checked. The assumptions block at the top records the settings used for that run.
It is the same file the pages are built from, not an export prepared separately, so there is no opportunity for the two to disagree. It is free to use for any purpose, including republication, with attribution to energycostmap.com. Anyone reproducing the method rather than the figures will find the formula set out above.
| Date | Change |
|---|---|
| 2026-10-04 | Dataset package on GitHub and Zenodo corrected. The deposited states.json carried placeholder values from a test build in which every state had the same generation and retail rate. The figures published here were never affected. The README is now generated from the data so the two cannot diverge again. |
| 2026-10-03 | Privacy page added, and security.txt corrected: it had stated that no personal data was collected while Google Analytics was running. |
| 2026-10-03 | Author, about page and per-page attribution added. |
| 2026-10-03 | Bordering-state links added to every state page, replacing a tile-grid distance that had listed Hawaii as a neighbour of Texas. |
| 2026-10-03 | Export-rate wording in the FAQ corrected on nine states. The FAQ tested a policy label while the body tested the export factor, so states crediting between 0.6 and 1.0 of retail were described as paying 'the full rate'. |
| 2026-09-24 | System size calculator published at /system-size/. |
| 2026-09-04 | All 50 states published. Illinois and Kentucky released last, once the Illinois Shines payout and the LG&E export rate from PSC Case 2021-00397 could be established from primary sources. |
| 2026-08-26 | Hawaii state tax credit corrected from $5,000 to $6,488 after a reader pointed out that the RETITC cap applies per 5 kW of capacity rather than per installation. The credit caps in the other four states with percentage-based credits were rechecked at the same time and were already correct. |
| 2026-08-26 | California self-consumption lowered to 45% under NEM 3.0, from the 65% used for other instantaneous-netting states. The default produced a payback well short of published California estimates. |
| 2026-08-22 | Non-bypassable charges modelled separately, covering New York's Customer Benefit Contribution, Connecticut's Solar Energy Adjustment and Alabama Power's capacity reservation charge. |
| 2026-08-15 | Page titles and FAQs retargeted after keyword research showed that "solar payback [state]" has almost no search volume while "solar panel cost [state]" has a great deal. |
| 2026-08-11 | First eight states published. Federal ITC set to $0 for every state: Section 25D expired on 31 December 2025 and no replacement has been enacted. |
| 2026-08-11 | Installed cost set to $2.85/W nationally, with per-state overrides where local pricing differs materially. |
This site is not an installer and sells nothing. Some outbound links to quotation services may earn a commission. That has no bearing on the figures: every number is produced by the process described above from public data, and no company can pay to alter one, to appear on a state page, or to be ranked higher.
Privacy. These are estimates for comparison between states, not financial advice and not a quotation for a specific property. Roof orientation, shading, consumption pattern, the serving utility's tariff and installer pricing all affect the result. At least three written quotations are advisable before committing.