You don’t need to wire panels yourself, and you shouldn’t. But understanding the basics helps you spot a bad design and ask your installer the right questions.
- Series adds up voltage, current stays the same.
- Parallel adds up current, voltage stays the same.
- Most home systems use series strings, sometimes two strings in parallel.
- The string must fit the inverter’s MPPT and max voltage limits.
Series: voltages add up
In series, the positive of one panel connects to the negative of the next, like batteries in a torch. The voltages add up, and the current stays the same as one panel.
Example: a panel with a working voltage (Vmp) of about 42V. Eight in series gives roughly 336V. Current stays around 13 to 14A, same as one panel.
Why installers like series: higher voltage means lower current for the same power, so thinner cables and lower losses over long runs. Most hybrid inverters also need a fairly high voltage to start tracking.
Parallel: currents add up
In parallel, all positives join together and all negatives join together. Voltage stays the same as one panel (or one string), and the currents add up.
Where parallel is used: joining two identical strings to one MPPT input, or in older low-voltage systems with 12V or 24V charge controllers.
Series-parallel: the common home setup
A 10kW home system might have two strings of nine panels each. Each string is in series, and the two strings either go to separate MPPT inputs or join in parallel at one input. This balances voltage and current to fit the inverter.
What about shading?
In a series string, the weakest panel can drag the whole string down. If a water tank shades two panels every afternoon, put those panels on a separate string or a separate MPPT so they don’t pull down the rest. Modern panels have bypass diodes that limit the damage, but layout still matters.
The rules your installer must follow
- String open-circuit voltage (Voc) on the coldest morning must stay below the inverter’s max PV voltage.
- String working voltage should sit inside the MPPT range.
- String current must not exceed the MPPT input current limit.
- Strings joined in parallel should have the same number and type of panels.
If you’d like to understand where these limits come from, read what MPPT is and how to read an inverter spec sheet.
Want us to check your string design?
Send the panel model, number of panels and inverter. We’ll verify it fits safely.