Series and Parallel Connection Calculator
Work out array voltage and current for any series and parallel panel arrangement, and check it against your inverter window.
Results
Series adds volts, parallel adds amps
Panels wired in series share the same current and add their voltages. Wired in parallel they share the same voltage and add their currents. Array power is the same either way; what changes is the wiring, the cable size and whether the string fits the inverter.
Check the cold morning, not the hot afternoon
Panel voltage rises as temperature falls, and the highest open-circuit voltage of the year happens on a cold, bright morning. String voltage has to stay inside the inverter window at that moment. Designing to the summer figure is how inverters get damaged in their first winter.
Common mistakes
Mixing panels of different current in one series string, or different voltage in one parallel group. In series the string is limited by the lowest current; in parallel the group is dragged to the lowest voltage. Either way the mismatch is paid for every day the system runs.
Questions people ask
Which is better for shading? Parallel, generally — a shaded panel drags its own string down in series. Optimisers or micro-inverters solve it properly.
When do parallel strings need fuses? From three strings upward, because the remaining strings can backfeed a fault in one of them.