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Solar Panel Array Sizing Calculator

Estimate how many solar panels you need to meet a daily energy usage target.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-25 · v1.0.0

Market
Imperial · sales tax

Solar panels needed

7 panels

Check your inputs

Actual output varies with roof orientation, tilt, shading, and seasonal sun-hour changes — a solar installer's site-specific production estimate (often via satellite/aerial modeling) is significantly more accurate than this general planning figure.

Estimated daily output per panel
1600 Wh

With the figures above, the solar panels needed comes to 7. Note that daily energy usage target sits at the low end of the range this calculator was checked against, so treat the output as indicative rather than settled. The method behind this is well established, though site conditions and material batches will move it somewhat. This is calculated for United States and cites IRC 2024. Building in another market? Change the selector above so the units and code reference follow.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Panels needed = daily energy target (Wh) / (panel wattage x average daily sun hours x system efficiency)

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

What are 'peak sun hours' if they're not the same as daylight hours?
Peak sun hours is a standardized measure of total solar energy received, expressed as the equivalent number of hours at maximum (1,000 W/m²) intensity — a location might have 12 hours of daylight but only 5 'peak sun hours' worth of usable solar energy.
Does roof orientation matter beyond what this calculator captures?
Yes significantly — south-facing (in the Northern Hemisphere), unshaded, properly-tilted roofs produce much closer to the theoretical maximum than east/west-facing or partially shaded roofs, which a general sun-hours average doesn't fully capture.
Should I size for 100% of my usage?
That depends on your goals and any net metering policy — some homeowners intentionally size smaller (offsetting a portion of usage) for a faster payback, while others aim for 100%+ offset where net metering rules allow banking excess production.