Quick definition
Series wiring connects panels or batteries end to end, the positive terminal of one linking to the negative terminal of the next, forming a chain called a string. In this configuration, each unit's voltage adds to the next, so a string's total voltage is the sum of every panel or battery in it, while the current stays the same as a single unit throughout the whole string.
This is the standard default configuration for most panel strings, since it efficiently builds up the voltage a system needs using standard cable gauges, without the higher current, and correspondingly thicker cabling, that a parallel configuration would require.
At a glance: the maximum number of panels or batteries that can be safely wired in series is limited by the connected inverter or charge controller's maximum voltage rating, a limit carefully calculated during system design.
Why it matters
Series wiring's voltage-building efficiency is exactly why it's the default choice for most string inverter systems. Building a system's required voltage through series connections uses standard, relatively affordable cable gauges, since current, the main driver of required cable thickness, stays constant regardless of how many panels get added to the string.
The real tradeoff is shading sensitivity. Because every panel in a series string shares the same current, one significantly shaded panel effectively limits the entire string's current to whatever that weakest panel can produce, dragging down the output of every other panel in the string along with it. Experimental research from NREL's Outdoor Test Facility documented this exact effect on a series-connected grid-tied string, confirming how even partial shading on one module measurably reduces the whole string's output. Bypass diodes help reduce this effect but don't eliminate it entirely, which is exactly why microinverters or power optimizers, architectures that avoid this shared-current limitation, are often chosen for roofs with meaningful shading challenges. To see Series wiring in a real example, the solar inverter size calculator in our Inverters & Equipment section applies it to a working system.
Understanding series wiring also helps explain why string sizing gets calculated so carefully during system design. Too many panels or batteries in one series string can push voltage beyond what the connected inverter, charge controller, or local electrical code allows. Section 690.7 of the National Electrical Code, NFPA 70, specifically requires that this maximum string voltage be calculated at the coldest expected temperature for the installation site, since panel voltage actually rises in cold weather, which is why installers work through specific voltage calculations rather than simply wiring every available panel into one long string.
Where you'll see this
The battery series configuration calculator works out how many batteries in series reach a target system voltage.
For a combined approach, the battery series parallel mixed configuration tool helps design a battery bank using both series and parallel wiring together.
For solar panels specifically, the string length voltage calculator works out the total voltage a given string of panels wired in series will produce, a key input for staying within an inverter's rated voltage window.
This term comes up in panel and battery wiring diagrams, in string sizing calculations during system design, and any technical explanation of how a system's overall voltage is built up from individual components.
Frequently asked
Series wiring efficiently builds up voltage using standard cable gauges, since current stays the same across the string rather than adding up. This makes it a practical, cost-effective default for connecting multiple panels into one string feeding a shared inverter.
Yes, to a real degree, since panels in a series string share the same current, and a shaded panel can't produce as much current as its unshaded neighbors, effectively limiting the whole string's output to what the weakest panel can handle. Bypass diodes reduce, but don't fully eliminate, this effect.
Yes, effectively set by the inverter or charge controller's maximum voltage rating and by local electrical code voltage limits. Adding too many units in series can push voltage beyond what the connected equipment or code allows, which is why string sizing is carefully calculated during system design.
Yes, this is a common approach, often called a series-parallel or mixed configuration. Multiple panels or batteries get wired in series to build a target voltage, and multiple series strings then get wired to each other in parallel to also reach a target current or capacity.