How many panels for your array
Work out how many solar panels of a given wattage you need to reach a target array size.
Solar panels are sold in fixed wattages, so a target array size in watts needs converting to a whole number of panels before you can price or wire a system — round up, since a slightly oversized array covers cloudy days and panel derating better than an exact match. Use the array sizing calculator first if you don't already have a target watt figure.
Related calculators
Looking for a definition or a quick answer? See the solar & battery glossary for terms used on this page, or the FAQ for common sizing questions.
Sources & standards
- NREL PVWatts Calculator — NREL's solar-production model; its default system-loss breakdown underlies the ~0.75 array loss factor used here.
- IEC 61215 — Terrestrial Photovoltaic (PV) Modules: Design Qualification and Type Approval — Design-qualification and durability testing standard for the solar panels used in array sizing.
Estimates for planning only. Verify with a meter and follow NEC / local code; have a licensed installer confirm any system before purchase or wiring. See the methodology for formulas and sources.