Planning with U.S. state data and USD. Translations do not change the market or currency.
Methodology
The calculator is designed for early planning. It uses transparent formulas and visible assumptions instead of claiming installer-grade precision.
Methodology updated 2026-09-30.
Source stack
Production evidence: California has a saved full PVWatts response; eight states have successful API yields recorded to two decimals. Colorado, Illinois and Pennsylvania retain explicit author assumptions. The download distinguishes these evidence levels.
$0.3361/kWh
33.61 ¢/kWh
EIA Table 5.6.A, July 2026 residential column; published September 24, 2026. Divide the published cents/kWh by 100. This preliminary statewide average is a fallback, not your utility tariff. Use your bill's energy-only rate; fixed charges remain payable.
1,595.2 kWh/kW/year
kWh/kW/year
PVWatts V8 typical-weather model at an author-selected reference point in the state: 4 kW DC, roof mount, 20° tilt, 180° azimuth, 14% system losses. Annual AC kWh ÷ 4 gives kWh/kW/year. Losses are already included and are not deducted again. Neither a statewide average nor a ZIP or roof survey. Shade and ±10% production bounds are separate author scenarios.
$1.98–$2.98/W
$2.48/W × 0.8…1.2
EnergySage's state marketplace average, table updated August 28, 2026. We calculate an author-selected range of average × 0.8 to average × 1.2, rounded to cents/W. This ±20% scenario is not an observed price distribution or confidence interval. Cash solar only, before incentives; compare like-for-like local quotes.
The 12-month editor requires a complete positive year; zero months are valid. Its exact monthly average feeds the sizing engine. Monthly usage stays in the current page and is not included in report URLs or saved scenarios. A seasonal balance uses the available PVWatts AC reference series normalized to the annual estimate, without applying losses a second time. Monthly energy differences do not establish imports, exports or tariff credits; interval matching is needed.
The fixed-rate loan tool uses the contract interest rate for amortization and keeps disclosed APR separate. Cash and financed prices must describe the same scope. A voluntary extra payment is applied after the selected scheduled month; a recast changes payments only when explicitly selected. No tax-credit paydown is assumed.
The bill worksheet models period imports × import rate minus exports × export rate, caps credits at energy charges, then adds fixed and other charges. Excess credits are shown separately. It does not replicate time-of-use prices, tiers, true-ups, a utility credit bank or household eligibility.
Production evidence: California has a saved full PVWatts response; eight states have successful API yields recorded to two decimals. Colorado, Illinois and Pennsylvania retain explicit author assumptions. The download distinguishes these evidence levels.
Original calculator output for 12 states × 3 direct-use shares (30%, 55%, 70%) × 3 export values (10%, 35%, 100% of retail). Every row uses 900 kWh/month, 400 W panels, low shade and a 100% annual energy target. This is a synthetic model comparison, not measured customer performance or a forecast of your tariff.
At 55% direct use and 35% export value, 100% energy coverage offsets this share of modeled energy charges: 70.75%
55% + 45% × 35% = 70.75%. Fixed charges are additional. This identity follows from the model's assumptions, not from observations.
| State reference | System size | Annual energy savings | Remaining energy charge |
|---|---|---|---|
| California | 6.8 kW | $2,568 | $1,062 |
| Texas | 6.6 kW | $1,213 | $502 |
| Florida | 7.0 kW | $1,148 | $475 |
| Arizona | 6.3 kW | $1,175 | $486 |
| Nevada | 6.2 kW | $976 | $403 |
| New York | 9.2 kW | $2,285 | $945 |
| New Jersey | 7.9 kW | $1,925 | $796 |
| Massachusetts | 8.3 kW | $2,330 | $963 |
| North Carolina | 8.1 kW | $1,158 | $479 |
| Colorado | 8.1 kW | $1,299 | $537 |
| Illinois | 10.0 kW | $1,469 | $607 |
| Pennsylvania | 10.0 kW | $1,660 | $686 |
Reproduce a row by entering its complete input object into the calculator. JSON includes inputs, formulas, source snapshots and limits; CSV contains all 108 results. The table below selects 55% direct use and 35% export. Data version: September 4, 2026.
Quick answer
It is a first-pass planning range built from your usage, a production assumption, visible system losses, direct solar use, export value, and gross cost benchmarks. It is not an engineering design, utility approval, tax determination, production guarantee, or installer quote.
| Label | Meaning | Use before a decision |
|---|---|---|
| Calculated estimate | A formula result based on entered and default assumptions. | Change assumptions and compare a range. |
| Manufacturer specification | A value published for a named equipment model. | Confirm the exact model and datasheet. |
| Government incentive | A program claim tied to an official source and eligibility rules. | Verify current status and personal eligibility. |
| Utility information | Tariff, export, interconnection, or billing terms from the serving utility. | Confirm the exact account and rate plan. |
| Installer quote | Project-specific price, equipment, scope, and production proposal. | Compare written assumptions and contract terms. |
Incentives are not applied by default unless they have a source URL, updated date, eligibility note, active status, and explicit inclusion in the data model. This is especially important for 2026 homeowner estimates after federal credit-status changes.
View sourcesOnce the assumptions make sense, run the calculator and keep the source notes handy when comparing installer proposals.