Sources & Methodology

CitySolarCosts.com provides city-level estimates of residential solar costs, annual production, savings, and simple payback. This page explains the types of sources we use, the assumptions behind our estimates, how we review and update content, and how you can report errors or ask questions.

Preferred source types

When researching and building estimates we prioritize primary, authoritative, and publicly available sources. Typical source types include:

Government and public data: national and state agencies that publish energy and weather data (for example: solar resource and irradiance datasets, electricity price statistics, and utility rate filings).
Utility and regulator documents: local utility rate schedules, net metering and interconnection rules, and public utility commission filings that affect billing and compensation for rooftop solar.
Incentive databases and program materials: official program pages, state/local rebate portals, and centralized incentive trackers.
Industry technical references: manufacturer specification sheets, inverter and panel performance data, and industry-standard loss/efficiency assumptions.
Peer-reviewed research and technical reports: studies on system performance, degradation, and modeling best practices.
Market data and installer surveys: aggregated pricing and installation-cost data from reputable market reports or aggregated installer data when available.

How we select and prioritize sources

We give priority to original, primary sources (official agency data, utility tariffs, program pages) when available.
Secondary sources (industry reports, market analyses) are used to supplement official data or to provide context where primary data is limited.
We prefer sources that are transparent about methodology and that provide downloadable or citable datasets.
Where local data is sparse, we rely on regional or state-level datasets and conservative assumptions, and we note where city-level interpolation is used.

Core methodology — how estimates are calculated

Our estimates are intended to be simple, transparent, and consistent across cities. The main calculation steps are:

Estimate typical system size for a residential installation in the area (in kilowatts).
Determine local solar resource: an average annual production factor expressed as kWh produced per kW installed (kWh/kW/year) using public irradiance datasets adjusted for typical system orientation and tilt.
Apply a performance ratio (system losses from wiring, inverter inefficiency, soiling, shading, and degradation) to produce a realistic annual production estimate.
Calculate annual production: system size (kW) × production factor (kWh/kW/year) × performance ratio.
Estimate annual savings: expected annual production × local average residential electricity rate (adjusted for net metering or local compensation rules where applicable).
Estimate installed cost: assumed installed price per watt × system size, then subtract publicly available incentives and rebates to get net upfront cost.
Simple payback: net upfront cost divided by estimated annual savings. This is a straight payback metric and does not account for financing costs, taxes, or alternative investment returns.

Key assumptions we typically use

Performance ratio to cover system losses and realistic operating conditions.
Standard degradation rate for panels over time (used for lifetime production estimates when relevant).
Installed cost per watt based on regional market data and public reports; local installer quotes may differ.
Local electricity rates based on publicly available utility or state averages; time-of-use rates and demand charges are handled conservatively or noted separately.
Incentives: we include widely available federal, state, and utility incentives when they are clearly documented; many incentives are time-limited or subject to change and are noted accordingly.

We publish the broad assumptions used for each city estimate, and where possible we link to the primary datasets or documents used.

Important limitations and caveats

Estimates are general and intended as an informational starting point. They are not a substitute for a site-specific site assessment or a formal quote from a licensed installer.
Actual system production depends on roof orientation, shading, tilt, local weather variability, and equipment choices.
Local utility billing rules, net metering policies, and time-of-use rates can materially change the economics; we aim to flag known policy differences but cannot model every rate plan.
Financing terms, tax situations, and personal financial circumstances are not modeled unless explicitly stated; users should consult financial or tax advisors for personal advice.
Incentive availability and program rules change frequently; check the original program webpages or your local authority for current details.

Research and fact‑checking process

Collect: our researchers assemble data from primary sources (utility tariffs, agency data, incentive program pages) and reputable secondary sources.
Document: each data point used in an estimate is logged with its source and date.
Cross-check: where possible we cross-check key values (electricity rates, solar resource) against multiple sources to spot inconsistencies.
Peer review: draft methodology changes and new modeling approaches are reviewed by the editorial team for consistency and plausibility.

AI assistance disclosure

We may use AI tools to help draft, summarize, or format content. Any AI-generated text is reviewed, edited, and validated by members of the City Solar Costs editorial team before publication. AI is used as an assistant, not as the final authority.

Human and editorial review

All pages and estimates are created, reviewed, and maintained by the CitySolarCosts.com Editorial Team. Content updates and methodological changes are reviewed by at least one editor on staff before being published. Guest contributions or contractor-provided analyses are labeled and reviewed for accuracy and alignment with our methodology.

How often content is updated

We review and update data and methodology on a regular schedule and when significant changes occur. Typical triggers for updates include:

Major changes to federal, state, or utility solar policies (for example, changes to tax incentives or net metering rules).
New or updated public datasets for solar resource or electricity prices.
Material changes in regional market pricing or installer cost benchmarks.

Where practical, pages include a “last updated” date so readers can see how current the information is.

Corrections and reporting errors

If you believe we have an error or omission, please let us know. Use our contact page (https://citysolarcosts.com/contact) or the contact form on that page to report corrections. Provide the page URL, the item you believe is incorrect, and any source documents that support your correction. We will investigate and, when appropriate, update the content and note the correction.

Independence and advertising disclosure

CitySolarCosts.com is editorially independent. We may display advertising, sponsored content, or links to third-party services. Any sponsored content or paid placement is clearly labeled. Where we use affiliate links or receive referral fees for products or services, we disclose that relationship on the relevant pages.

Author and byline approach

Content is produced under the byline “CitySolarCosts.com Editorial Team.” When applicable, articles will note if external contributors or guest authors provided material, and any significant interests or affiliations will be disclosed alongside the content.

Contact

To ask about sources, request data, or report an error, please use our contact page: https://citysolarcosts.com/contact. If you prefer, use the contact form on that page and the editorial team will respond.

Disclaimer (site-specific)

The estimates and information on CitySolarCosts.com are provided for general informational purposes only. They are not professional financial, tax, legal, or installation advice and should not be relied on as the sole basis for making decisions. Actual solar system performance, costs, incentives, and payback periods depend on site-specific conditions, local regulations, finance terms, and individual circumstances. Always obtain multiple, written quotes from licensed solar installers and consult qualified advisors before making decisions based on the information on this site.

Published and maintained by the CitySolarCosts.com Editorial Team.