When you wire in series there is just a single wire leading from the roof for each string of solar panels.
How do you wire solar panels together.
The positive wires are connected to a positive connector within a combiner box and the negative wires are connected to the negative connector.
When a solar installer wires your solar panels in a series each panel is connected to the next in a string the total voltage of each solar panel is summed together but the amps of electrical current stay the same.
The parallel connection allows to increase the current keeping the same voltage.
When solar panels are wired in parallel the positive terminal from one panel is connected to the positive terminal of another panel and the negative terminals of the two panels are connected together.
For more information visit the page how to wire solar panels in parallel.
If we have two or more solar panels with the same voltage but with different current it is not possible to wire them in series.