Methodology

TrueSolarCost publishes calculator-driven research on residential solar economics. Every threshold, formula, and benchmark on the site comes from a primary public source. We cite by name on the page that uses the number, with a verification date stamped on the citation.

Sourcing tiers

Tier 1 — primary regulatory and scientific. NREL PVWatts (production estimates and NSRDB irradiance), EIA Electric Power Monthly (residential rates and escalator reality check), IRS Form 5695 / Residential Clean Energy Credit (tax-credit eligibility), LBNL Tracking the Sun(installed $/W bands and dealer-fee range), and the DOE Homeowner's Guide to Going Solar (consumer-protection framing). DSIRE is referenced as a pointer for state and utility incentive lookup; we do not make automated state-law claims downstream of it.

Tier 2 — authority explainers.SEIA industry data used only for adoption numbers, never for advocacy claims. LBNL Electricity Markets & Policy reports. Peer-reviewed solar economics papers.

Tier 3 — specific-fact and contract-language. Installer warranty terms cited from public spec sheets when relevant. IRS and FTC enforcement actions when a specific dealer-fee abuse is on the public record.

We do not cite as authority: EnergySage, SolarReviews, Solar-Estimate, Forbes Home Solar, or any installer-affiliated brand-roundup content. These are competitors and lead-gen funnels, not primary sources.

Calculator inputs and formulas

Each calculator page exposes its inputs, the formula behind the output, and the public source for every constant in the math. The quote calculator additionally surfaces verdict reasoning — which threshold a number tripped, and the source of that threshold — so a reader can audit the audit itself.

Review cadence

IRS guidance and EIA rate releases are re-verified before any publish that surfaces them. NREL and LBNL inputs (production ranges, $/W bands) are re-verified quarterly. DSIRE pointers are re-verified whenever the relevant state surface is touched. Each page lists an Updated date that reflects the most recent re-verification, not the build date.

What we don't do

We don't fabricate homeowner anecdotes. We don't cite publication numbers we haven't verified. We don't present AI-generated rooftops as photographs. When a calculation has a known uncertainty (10-year vs short-term rate escalator, regional production variability, dealer-fee range) we state both bounds rather than rounding to the optimistic one.

Questions or corrections? Contact us.