What is the difference between series and parallel?
It is all about which number stacks. In **series** you connect the positive of one panel to the negative of the next, like links in a chain, and the **voltages add while the current stays the same**. Two 20-volt, 10-amp panels in series make 40 volts at 10 amps. In **parallel** you tie all the positives together and all the negatives together, and the **currents add while the voltage stays the same**: those two panels make 20 volts at 20 amps.
Either way the power is identical, because **watts equal volts times amps** and 40 by 10 equals 20 by 20 equals 400 watts. You are not gaining or losing energy by choosing one; you are choosing whether the system runs at high voltage and low current or low voltage and high current.
How shade changes the math
This is the deciding factor for many people. In a **series** string, the panels share one current path, so the **weakest, most-shaded panel throttles the entire string**. One panel under a branch can drag down everything wired with it. In **parallel**, each panel feeds the system on its own, so a shaded panel **only loses its own output** and the rest keep producing.
That makes parallel the more forgiving choice on a roof or campsite with partial shade. Series wins where sun is even and unobstructed, where its higher voltage and thinner wiring are an advantage rather than a liability.
Which should you use?
Match it to your charge controller and system voltage. An **MPPT controller** thrives on higher input voltage, so it pairs well with **series** (or a series-parallel mix), and the higher voltage lets you use thinner, cheaper wire over a long run with less loss. A basic **PWM controller** or a **12-volt battery system** wants the array voltage kept close to the battery, which points to **parallel**.
Most larger arrays actually use **series-parallel**: panels grouped into series strings, and those strings paralleled together, to balance voltage, current, and shade tolerance. Whatever you choose, keep the array's voltage and current inside your controller's and inverter's rated windows. Shopping for panels to wire up? See best portable solar panels.
Series wins on
- +Higher voltage, so thinner wire and less loss over long runs.
- +Ideal for MPPT controllers and grid-tie strings.
- +Fewer connectors and no per-panel fusing.
Parallel wins on
- +Shade on one panel does not tank the rest.
- +Keeps voltage low for 12V battery and PWM systems.
- +Easy to add one more panel without raising voltage.
The verdict
Use series, or a series-parallel mix, with an MPPT controller for efficiency, higher voltage, and long wire runs in even sun. Use parallel for low-voltage 12V or PWM systems and for roofs or campsites with partial shade, where one shaded panel should not drag down the rest. Most big arrays combine both. The non-negotiable is keeping the array's voltage and current within your charge controller's and inverter's rated limits.
Related: Best portable solar panels, Solar panel calculator.
Frequently asked questions
Is it better to wire solar panels in series or parallel?
Neither is better in general; they produce the same power. Series adds voltage and suits MPPT controllers, long wire runs, and even sun. Parallel adds current, keeps voltage low for 12V and PWM systems, and is more shade-tolerant because one shaded panel only loses its own output. Match the choice to your charge controller and your shade.
Does series or parallel charge a battery faster?
It depends on your charge controller. With an MPPT controller, a higher-voltage series array often charges more efficiently, especially over long wire runs. With a PWM controller on a 12V battery, parallel keeps the voltage usable. The power is the same either way, so the controller type, not the wiring alone, drives charging speed.
What happens to series panels in the shade?
Because series panels share one current path, the most-shaded panel limits the current for the whole string, so even one shaded panel can sharply cut the string's output. This is the main drawback of series and the main reason to use parallel, or a series-parallel layout, where partial shade is likely.
Can I mix series and parallel?
Yes, and large arrays usually do. You group panels into series strings to raise voltage, then connect those strings in parallel to add current. This series-parallel layout balances voltage, current, and shade tolerance. Keep the total voltage and current within your charge controller's and inverter's rated windows.
Does series or parallel give more power?
Neither. Power equals voltage times current, and series and parallel just trade one for the other, so the wattage is the same. The real differences are voltage and current levels, wiring and fusing needs, shade behavior, and which charge controller the array suits.