The EcoGen Solar Database: How Our Numbers Are Built
Every cost, payback and system-size number on this site resolves from one table covering all 50 states and Washington DC, not from a figure written by hand on each page. This page shows you what goes into that table, what the calculations assume, and where each input came from, so you can check our arithmetic against your own quote.
Most solar cost pages give you a number and no way to test it. Two sites quote the same state $1,000 apart, neither says why, and you are left guessing which one describes the quote sitting on your kitchen table.
We built the EcoGen Solar Database to remove that guesswork from our own writing first. It is a single normalized table covering all 50 states and Washington DC. Every state page pulls its price per watt, its national rank, its typical system size and its payback years from that one row, which means a Connecticut figure and a Texas figure are built the same way and can be compared honestly. This page is the full account of how it works.
What the EcoGen Solar Database Contains
The Database is the umbrella. Underneath it sit four named components, each answering a different question and each carrying its own sources and dates.
EcoGen Solar Cost Index
The standardized installed price per watt for a state, before any incentive. Every cost figure we publish is this number multiplied out, and every “cheaper than average” or “more expensive than average” claim is this number compared against the national row.
EcoGen Solar Payback Methodology
The fixed rule set behind every payback year and every 25-year savings figure. The assumptions are versioned, so a payback number published in March and one published in August were produced by the same model or they say which version they used.
State Profile
The household picture for each state: average monthly consumption, the residential electricity rate, the resulting monthly bill, the solar production a kilowatt actually delivers there, and the system size that combination calls for.
EcoGen Installer Index
The installer side of the Database: who serves which state, what each company publishes about itself, and what the state licensing registry says when we look the number up ourselves. Ranking weights for installers are published separately on each state’s companies page.
How the EcoGen Solar Cost Index Is Built
The Cost Index answers one question: what does a residential system actually cost per watt installed in this state right now, before incentives. The current method is version 2, and it works in four steps.
Step 1: Blend two national marketplace price sets
The state price starts as a weighted blend of the two largest published solar marketplace price sets, EnergySage and SolarReviews. Neither is treated as authoritative on its own, because they consistently disagree, and the size of that disagreement is itself useful information.
Pennsylvania is a worked example. The two sources reported $2.63 and $3.16 a watt. Weighted 60/40, that produces $2.84 a watt, which is the number every Pennsylvania cost figure on this site is built from.
Step | Pennsylvania | What it means |
|---|---|---|
EnergySage, weighted 60% | $2.63/W | Contributes $1.58 |
SolarReviews, weighted 40% | $3.16/W | Contributes $1.26 |
Blended Cost Index | $2.84/W | The published figure |
Divergence between sources | 18.3% | Flagged, above the 15% threshold |
Cost per kW installed | $2,840 | Index multiplied by 1,000 |
National rank | 24 of 51 | 2.1% below the national average |
Step 2: Flag the states where the sources disagree
When the two price sets diverge by more than 15%, the row carries a divergence flag. Pennsylvania’s 18.3% gap is flagged. The flag does not change the published number, but it does tell our writers that quotes in that state spread unusually wide, which is worth saying out loud on the page rather than hiding behind a single average.
Step 3: Cross-check against transacted prices where they exist
Marketplace prices are quoted prices. Where Lawrence Berkeley National Laboratory’s Tracking the Sun data covers a state, we compare the blended figure against what systems actually sold for. Where there is no coverage, the row records that plainly rather than implying a check happened. Pennsylvania has no Tracking the Sun coverage in the current release, so its confidence is recorded as triangulated rather than transacted.
Step 4: Rank every state against the same national row
Each state gets a rank from 1 to 51 and a percentage difference against the US average. This is the part that stops a common failure. A state page written in isolation will claim its state is “below the national average” because it sounds reassuring. Here the rank is computed from the table, so a state is only called cheap when the arithmetic says so. North Dakota sits at rank 51 and 32.1% above average, and its page says exactly that.
The Payback Assumptions, Published in Full
Payback periods are only as honest as the assumptions underneath them, and most published payback numbers never show theirs. Ours are fixed in a versioned assumption set. The current version is v1-2026, and every payback figure on this site was produced with it.
Assumption | Setting in v1-2026 | Why it is set this way |
|---|---|---|
Federal credit, systems you buy | 0% | The 30% Section 25D residential credit ended for systems completed after December 31, 2025. Modeling it would overstate savings. |
Federal credit, leases and PPAs | Section 48E only | A third party that owns the system can still claim a commercial credit. The homeowner does not. |
Electricity rate escalation | The state’s own 5-year growth rate, floored at 2% and capped at 4% | Using each state’s actual recent history beats a single national guess. The floor and cap stop an unusual few years from producing a fantasy payback. |
Panel degradation | 0.5% per year | Standard manufacturer warranty territory. Production falls slightly every year and the model reflects it. |
Horizon | 25 years | Matches typical equipment warranty length, so the savings figure covers a period the equipment is warranted for. |
Where the State Profile Numbers Come From
System size, monthly bill and production are not estimates we invented. Each traces to a named public source with a retrieval date, and the derived figures are simple arithmetic on those inputs.
Figure | Source | As of |
|---|---|---|
Residential electricity rate | EIA Electric Power Monthly, Table 5.6.A | March 1, 2026 |
Average monthly consumption | EIA Electric Power Monthly | March 1, 2026 |
Solar production factor | NREL PVWatts, run at each state’s largest city | June 2026 |
Net metering and export credit | State utility commission orders, tariffs and statutes | June 10, 2026 |
Lease and PPA legality | DSIRE Third-Party Solar PPA map | May 2026 |
Median home value | US Census ACS 2024 1-year, table B25077 | June 10, 2026 |
Marketplace prices | EnergySage and SolarReviews, blended 60/40 | June 11, 2026 |
Three figures are calculated rather than sourced, and you can reproduce all three:
- Average monthly bill is monthly consumption multiplied by the residential rate. Pennsylvania: 817 kWh at 20.43¢ gives $166.91.
- Typical system size is annual consumption divided by the production factor. Pennsylvania: 9,804 kWh a year divided by 1,399 kWh per kW gives 7.01 kW.
- Typical system gross cost is that system size multiplied by the cost per kW. Pennsylvania: 7.01 kW at $2,840 gives roughly $19,900 before tax.
Published figures are rounded, so recomputing from the rounded inputs on a page can land a few dollars away from the stored value. That is rounding, not a different number.
See What These Numbers Look Like for Your Own Home
State averages are a starting point, not a quote. Your roof, your usage and your utility move the answer. Enter your ZIP code to see the size, cost and payback these same figures produce for your address.
Try our solar cost and savings calculator!
What We Deliberately Do Not Do
A methodology is defined as much by its refusals as by its formulas.
- No company pays for a ranking or a listing. Whether a company buys leads from us has no influence on its position anywhere on this site.
- No stored star ratings. Live review scores may appear on a card, but they never feed a stored score, and we do not keep our own copy of them.
- No invented precision. Where a source does not cover a state, the row says so. “Not checked” appears in our records instead of a plausible guess.
- No statistic from unverified records. We are building a licence-verification series by looking numbers up in state registries ourselves. Rows that have not been checked against a registry are marked as such and are excluded from any published figure.
How Often the Numbers Change
Electricity rates move quarterly, marketplace prices move monthly, and incentive rules move whenever a legislature acts. Rate and price inputs are refreshed on a monthly cycle. Policy fields, meaning net metering, export credit, lease and PPA legality and licensing, are re-checked against primary sources when the underlying source publishes an update. Every field carries its own as-of date, so a page never implies a figure is fresher than it is.
When the assumption set itself changes, it gets a new version number rather than a silent edit. Anything published under v1-2026 stays traceable to the rules listed above.
Frequently Asked Questions
It is the standardized installed price per watt for a state before incentives, blended 60/40 from the two largest published solar marketplace price sets and ranked against all 50 states and Washington DC. Every cost figure on this site is calculated from it rather than written by hand.
Because most sites publish a single source and we publish a blend, and because we apply the same method to every state. Where our two price sources disagree by more than 15%, we flag it rather than hiding the spread inside an average. Pennsylvania’s sources differ by 18.3%, which is why quotes there vary so widely.
Assumption set v1-2026: no federal credit on systems you buy outright, Section 48E for leases and PPAs only, electricity rate escalation set to each state’s own 5-year growth rate floored at 2% and capped at 4%, 0.5% annual panel degradation, and a 25-year horizon.
Rate and price inputs refresh monthly. Policy fields such as net metering, export credit and lease legality are re-checked when the underlying primary source publishes an update. Every field carries its own as-of date, and changes to the assumption set get a new version number.
No. Whether a company buys leads from us has no influence on its ranking or its presence anywhere on this site. Installer ranking weights are published on each state’s companies page.
Yes, and that is the point of this page. The sources are named with retrieval dates, the blend weights are published, and the three derived figures are plain arithmetic: bill equals consumption times rate, system size equals annual consumption divided by production factor, and gross cost equals system size times cost per kW.
Sources
References & Research Sources
EcoGen America built the Database described on this page from federal energy statistics, national laboratory modeling tools, state utility commission records, federal tax guidance, and published solar marketplace pricing. Retrieval dates are listed against each source below and against each field in the table above.
- US Energy Information Administration (EIA). Electric Power Monthly, Table 5.6.A, Average Price of Electricity to Ultimate Customers by End-Use Sector. Federal source for state residential electricity rates and average household consumption. Data as of March 1, 2026.
- National Renewable Energy Laboratory (NREL). PVWatts Calculator. Federal modeling tool used to derive the annual production factor for each state, run at the state’s largest city with stored coordinates. Accessed June 2026.
- Lawrence Berkeley National Laboratory (LBNL). Tracking the Sun. Federal research series on transacted residential solar system prices, used as a cross-check where state coverage exists. Accessed June 2026.
- DSIRE, NC Clean Energy Technology Center. Third-Party Solar PPA Map, May 2026. Reference source for lease and power purchase agreement legality by state. Retrieved June 10, 2026.
- US Census Bureau. American Community Survey 2024 1-Year Estimates, Table B25077, Median Value of Owner-Occupied Housing Units. Federal source for state median home value. Retrieved June 10, 2026.
- State public utility commissions and legislatures. Net metering orders, export credit tariffs, contractor licensing statutes. Primary-source research per state covering net-metering regime, export credit rate and licensing requirements. Retrieved June 10, 2026.
- Internal Revenue Service (IRS). FAQs for Modification of Sections 25C, 25D, 25E, 30C, 30D, 45L, 45W and 179D under Public Law 119-21. Federal guidance confirming termination of the residential clean energy credit for installations completed after December 31, 2025. Accessed August 4, 2026.
- EnergySage and SolarReviews. Published state-level residential solar pricing. The two marketplace price sets blended 60/40 to produce the Cost Index. Retrieved June 11, 2026.