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Solar Inverter Sizing Calculator

Size an inverter to an array, including the deliberate over-sizing of DC to AC that improves real yield.

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 2026-08-27 · v1.0.0

Market
Imperial · sales tax

Inverter AC rating

5000 W AC

Check your inputs

Capacity sizing only. String voltage limits, MPPT window, temperature coefficients and the local wiring rules all constrain the final selection.

Inverter rating
5 kW AC
Array DC rating
6 kW DC
Realistic peak AC after losses
5.16 kW
Headroom over realistic peak
-3.1 %

At the values currently entered, the inverter ac rating works out to 5000 W AC. Note that array dc rating (w) sits at the low end of the range this calculator was checked against, so treat the output as indicative rather than settled. Confidence is moderate: the method is sound, but real materials and site conditions vary. Figures are shown for United States, where IRC 2024 is the governing residential reference; switch the market above if you are building elsewhere.

Add the equipment this sizes

This result is a specification — 5,000 W AC — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

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

  • DC-to-AC ratio (ILR) of 1.1-1.3 is standard practice; NREL SAM documentation and inverter manufacturers' design guides
  • IEC 62109 and local wiring rules govern the electrical design; this sizes capacity only

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Frequently asked questions

Why is the inverter smaller than the array?
Because the array almost never produces its nameplate. Standard Test Conditions are 1000 W/m² at 25 °C cell temperature, which in the field happens for a handful of hours a year — panels run hot and lose output as they do. An inverter matched to the nameplate is idle capacity for the whole rest of the year, so the array is deliberately over-sized against it.
Does over-sizing waste energy?
A little, at the very top. When DC output exceeds the inverter's rating it clips, and that energy is lost. At a 1.2 ratio the clipping loss is typically well under 1% annually, against a much larger gain in the many partial-output hours. Above about 1.3 the trade starts running the other way.
What actually limits inverter choice?
String voltage more often than power. The array's open-circuit voltage rises as temperature falls, and the cold-morning figure must stay inside the inverter's maximum input — exceeding it damages the unit. Power sizing is the easy half of the problem; the voltage window is the half that needs the panel's temperature coefficient and your local record low.