Solar Sizing
Series / Parallel Array Configuration Calculator
Work out string voltage, current and array watts
Updated July 12, 2026 · Live
What this tool does
Calculates string voltage, total current and array power from panel Voc/Isc and how many panels sit in series and parallel.
Enter panel Voc and Isc and the number of panels in series and strings in parallel; the calculator returns string voltage, total current and array watts.
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Formula Used
How the series / parallel array configuration works
Panels wired in series add their voltages, so string voltage is the panel Voc times the number in series. Strings wired in parallel add their currents, so total current is the panel Isc times the number of strings. The open-circuit nameplate power is string voltage times total current. This is a topology check, not a wire-gauge calculation.
What you enter
Enter panel Voc and Isc and the number of panels in series and strings in parallel; the calculator returns string voltage, total current and array watts. Every field is editable, and the result recalculates the moment you change a value.
Reading the result
Use the string voltage to confirm it stays under your controller or inverter’s maximum input voltage — remembering that Voc rises in cold weather. Use the total current to size how many parallel strings a combiner must handle.
Safe by design
This calculator does the arithmetic of sizing — quantities, geometry and cost. It deliberately stops at the line a certified installer must sign off. It will never tell you a cable or fuse size, an earthing arrangement, a battery charge voltage, or a roof structural load: those are regulated calculations where a wrong number causes fire, electrocution or collapse. All electrical work must be carried out by a qualified, certified installer, and this page is not an installation guide.
Assumptions and limits
This draws the electrical topology only. It does not size string fuses, combiner boxes, cable or isolators — those are regulated and belong to a certified installer. Voc rises as temperature falls, so a string that is safe in summer can over-volt a controller on a cold, bright morning.
Using it with the rest of BuildMetricLab
This calculator is one step in planning a system. Pair it with the other solar sizing, geometry and cost tools to go from an energy figure to a panel count, a layout and a costed bill of materials. Every BuildMetricLab tool runs entirely in your browser — no sign-up, nothing sent to a server, and the formula is shown on the page so the maths can be audited.
Sources & methodology
Calculates string voltage, total current and array power from panel Voc/Isc and how many panels sit in series and parallel. Every result is calculated from the values you enter, all inputs are editable, and no time-sensitive prices or tariffs are embedded.
Frequently asked questions
What is the difference between series and parallel?
Series wiring adds voltage and keeps current the same; parallel wiring adds current and keeps voltage the same. The mix sets the string voltage and total current the controller sees.
Why does cold weather matter?
Panel open-circuit voltage rises as temperature drops. A string sized on the summer figure can exceed a controller’s maximum input voltage on a cold, clear day, so leave a margin.
Is the array watts figure the real output?
It is the open-circuit nameplate product of Voc and Isc, which overstates working output. Real power at the maximum-power point is lower; use it as an upper bound.
Does this tell me the cable size?
No. Conductor sizing, fusing and combiner design are regulated calculations for a certified installer — this tool stops at the topology.
Spotted something off?
Calculations or display — let us know.