Frequently Asked Questions

Yes. All 20 calculators are free to use without an account, without an email address, and without dismissing a lead-capture popup. Revenue comes from contextual display ads served only after you accept analytics cookies, plus future clearly-labeled affiliate links to authoritative information sources.

Yes. GainTally has no installer partnerships, no referral relationships with solar or EV brands, and no investor pressure to optimize for conversions. The calculator gives the same answer whether you install solar this year or wait five years. See our Author page for the no-lead-gen philosophy.

Advertising is served through Google AdSense — contextual display ads matched to content, not to your calculator inputs or personal data. Ads only appear after you actively accept analytics cookies via the cookie consent banner. We never target ads based on your calculation results. See our Privacy Policy for full details.

Two revenue streams: (1) contextual display advertising through Google AdSense, which requires your explicit cookie consent; and (2) future clearly-labeled affiliate links to product information pages. We do not sell leads, referral data, or calculator outputs to third parties. Our About page explains the model in full.

No. GainTally does not sell solar panels, quote installations, or earn commission on any clean energy purchase. We have no financial relationship with solar installers, distributors, or manufacturers. The calculator gives the same result whether you install solar this year, wait five years, or decide it is not right for your home.

No personally identifiable data is collected during calculations. Inputs you enter — zip code, system size, electricity rate — are processed entirely in your browser and never stored on our servers. Data needed for calculations (NREL solar irradiance, EIA electricity rates) is fetched from federal APIs without transmitting your inputs. If you opt into analytics via the cookie consent banner, Google Analytics 4 receives anonymized, aggregated events — not your specific inputs. Recent calculations are saved locally in your browser's localStorage and are never shared with installers, marketers, or any third party.

GainTally is a bootstrapped independent publisher with no venture capital, no outside investors, and no acquisition pipeline. There is no financial pressure to make payback periods look shorter than they are, or to route you to a preferred installer. Revenue comes from contextual display advertising and, in the future, clearly labeled affiliate links — neither depends on whether your calculation says yes or no to a purchase. See our About page for the full independence model.

Solar irradiance comes from NREL's PVWatts API; electricity and gas rates from the EIA open data API; appliance efficiency from EPA ENERGY STAR; tax credit guidance from the IRS. Every source is listed on our Citations page with direct links to each authority.

Federal API data (NREL solar irradiance, EIA electricity rates) is refreshed automatically. Static content — tax credit percentages, appliance benchmarks, state incentive rules — is reviewed and updated at least annually. Each page displays a “Last Updated” badge so you can see exactly when data was last verified. See our Methodology page for refresh cadence details.

Not at this time. All 20 calculators are browser-based and designed for individual homeowner use. We use NREL's PVWatts and EIA's open data APIs as our upstream sources — links to those public APIs are available on our Citations page.

Calculator inputs are processed entirely in your browser — we do not store your zip code, energy usage, or financial inputs on our servers. The only data transmitted is anonymized analytics after opt-in consent. Full details are in our Privacy Policy.

We use Consent Mode v2 (IAB TCF v2.3). Analytics and advertising cookies are opt-in only — they are off by default and only activate after you explicitly accept via the cookie banner. You can revoke consent at any time. See our Privacy Policy for the full cookie list.

Yes. We follow Consent Mode v2 (IAB TCF v2.3) with default-denied analytics and ads until you actively opt in. We do not sell personal information, we anonymize IP addresses in analytics, and we honor Global Privacy Control signals. Full details are in our Privacy Policy.

Primarily US homeowners evaluating major clean energy investments — solar panels, EV purchases, heat pumps, insulation upgrades. The typical use case is a $10,000–$40,000 decision that benefits from transparent, unbiased numbers before talking to any contractor or dealer. Browse our Glossary if any term is unfamiliar.

No functional difference. All 20 calculators are fully responsive and work identically on smartphones, tablets, and desktops. Input sliders are touch-optimized for mobile. Chart outputs are designed to be readable at small screen sizes.

Partially. The calculators themselves work without internet once the page has loaded. However, live NREL and EIA API data lookups require a connection. If you are offline, calculators fall back to state-level average data so you can still get meaningful estimates.

Our formulas produce estimates within documented benchmark ranges — typically ±10% for solar ROI and ±5% for EV total cost of ownership. Every formula is based on authoritative federal sources and validated against published research. See our Methodology page for benchmark tolerances.

Yes. Every formula, assumption, and data source is documented on the Methodology page — publicly readable without an account. Key assumptions such as panel degradation rate, utility rate escalation, and battery round-trip efficiency are exposed as adjustable inputs wherever possible so you can model your own scenario.

We validate formulas against NREL's System Advisor Model outputs and peer-reviewed studies on solar payback periods, EV total cost of ownership, and heat pump savings. Our Methodology page documents benchmark sources and acceptable deviation thresholds for each calculator.

Use the email on the About page. Describe the calculator, the inputs you used, your zip code, and what result you expected. We investigate all bug reports and typically resolve calculation errors within one business week. We do not offer a public issue tracker.

We occasionally collaborate with academic researchers, energy nonprofits, and independent journalists on clean energy data projects. If you have a research collaboration proposal, contact us via the About page. We do not accept sponsored content, guest posts, or paid placements.

Yes — we welcome suggestions. Use the contact link on the About page. Describe the calculation you need, the data sources you think are most authoritative, and the decision it would support. We evaluate all suggestions against our independence criteria before adding to the roadmap.

Not currently. Future affiliate links — if added — will be clearly labeled with “Affiliate Link” disclosure and will only link to authoritative information pages such as manufacturer specifications or government program pages. We will never add affiliate links to calculator recommendation outputs.

Currently none. We have no active installer referral partnerships, no solar or EV brand sponsorships, and no lead-generation relationships with any company. Any future partnership will be disclosed on the Author page before it affects site content.

No. We have no installer referral partnerships, no kickbacks tied to calculator outputs, and no investor pressure to optimize for conversions. The calculator gives the same answer whether you install solar this year or wait five years. See our Author page for the no-lead-gen philosophy.