About SolarCalculatorHQ

Last reviewed: 25 August 2026

What this site is

SolarCalculatorHQ is an independent publisher of free residential solar photovoltaic planning calculators. The public collection is intentionally small: system and panel sizing, energy output, fixed-panel tilt, off-grid and hybrid planning, RV and portable systems, inverter selection, pool heating, equipment comparisons and cost estimation.

The current public edition is English (United States) only. Draft translations and additional calculator source remain outside production until each page has an interface review, a source review and a worked result check. Their existence in the source repository is not a claim that they are ready for readers.

Editorial methodology

Calculator pages publish the formula, assumptions and practical limits needed to interpret the result. We prefer government, standards-body, national-laboratory and program-administrator sources for numerical or time-sensitive claims. Market reports and manufacturer documents are used only where primary public data is unavailable. A rule of thumb is identified as an estimate rather than presented as a code requirement.

Detailed photovoltaic yield pages follow the NREL PVWatts framework; simpler tools use clearly labelled peak-sun-hour or performance-ratio inputs. Outputs therefore depend on the location and loss assumptions entered by the user. For a contract decision, compare the estimate with a site-specific production model and an installer proposal.

Fixed-panel tilt pages use latitude-based estimates as a starting point and explain how seasonal objectives can change the angle a user compares. These are screening estimates, not site-specific optimisations; roof geometry, shading and hourly solar resource can change the best feasible tilt.

Cost tools use dated defaults and user-entered values, not a live quote, tariff or incentive feed. Readers should replace every planning default with a current local quote before making a purchase decision.

Publication gate

A page is public only when its calculator component and explanatory article agree on defaults and formulas, consequential claims have nearby sources, a worked example reproduces the displayed result, limitations are visible, and every internal link resolves to another reviewed page. Pages that fail any check are removed from routes, navigation and the sitemap rather than padded with generic prose or left indexable with a disclaimer.

Electrical protection, structural loading, fire, lightning, permitting and tax-determination tools are not part of the current public set. Those topics can produce false confidence when reduced to a short form, so they require qualified domain review before publication.

Review and update process

Time-sensitive pages show a published or reviewed date. We prioritise material changes to tax rules, incentive eligibility, regulated tariffs, code references and calculation defaults. Publication dates are not a promise that every market value changes in real time. If a page conflicts with its linked authority, the authority controls and the page should be reported for correction.

Funding and conflicts of interest

The site may be funded by display advertising served through Google AdSense. We do not run affiliate links to installers, equipment manufacturers, or financing providers. We do not sell or share user data. We do not accept paid placements, sponsored guides, or installer-network referral arrangements. If we ever add affiliate links to a piece of content, that content will be marked clearly at the top of the page.

Corrections policy

If you find a math error, a stale tariff, an outdated code reference, or a citation that no longer resolves, please email contact@solarcalculatorhq.com. We assess reports against the best available source. Confirmed material errors are corrected and the page review date is changed so readers can see when the current version was checked.

Common questions about our methodology

We are sometimes asked why our results differ from a quote a homeowner received from an installer. The most common reasons are: the installer modelled a different array tilt or azimuth than the user entered, the installer used a different irradiance source (often a postcode-level average rather than a TMY3 dataset for the specific location), the installer applied a different system-loss assumption, or the installer's quote includes financing costs we treat as a separate calculation.

Battery autonomy calculations are sometimes questioned for being conservative. A retained tool may start with 50 percent depth of discharge for lead-acid or 80 percent for lithium iron phosphate, but these are editable planning assumptions, not universal warranty limits. The battery manufacturer's current data sheet and battery-management settings control.

Limits

A calculator returns an estimate, not a quote. Site-specific factors including shading, roof condition, electrical service capacity, local permitting, and utility interconnection rules affect every real installation. Always confirm with a licensed installer before ordering equipment or signing a contract. The estimates on this site are not a substitute for engineering judgment, are not legally binding, and should not be used to support a building permit application without independent review.

Contact

Questions, corrections, or suggestions for new calculators? Email contact@solarcalculatorhq.com or use the contact page. The single address handles general enquiries, editorial questions, privacy requests, and partnership messages.