How to Wire Solar Panels: Series vs Parallel — Complete Guide

Understanding Series and Parallel Wiring

How you wire your solar panels determines the voltage and current delivered to your inverter. Getting this right is critical for system safety, inverter compatibility, and maximum energy harvest.

Series Wiring

In a series connection, you connect the positive terminal of one panel to the negative terminal of the next. This adds the voltages while the current stays the same.

• Voltage: Adds up (V₁ + V₂ + V₃...)
• Current: Stays the same as one panel

Example: 3 LONGi Hi-MO 7 Panels in Series

Vmpp per panel: 43.5V | Impp per panel: 13.56A

String output: 130.5V at 13.56A = 1,770W

Parallel Wiring

In parallel, you connect all positive terminals together and all negative terminals together. This adds the currents while voltage stays the same.

• Voltage: Stays the same as one panel
• Current: Adds up (I₁ + I₂ + I₃...)

Example: 3 Hi-MO 7 Panels in Parallel

Output: 43.5V at 40.68A = 1,770W

Series-Parallel (Hybrid) Wiring

Most systems use a combination: panels wired in series to form strings, then strings wired in parallel. This balances voltage and current to match the inverter's input range.

Example: 20 Hi-MO 7 Panels (2 strings of 10)

Each string: 435V at 13.56A

Two strings in parallel: 435V at 27.12A = 11,800W

How to Size Your Strings

Maximum String Length

Your string's maximum Voc (at coldest temperature) must not exceed the inverter's maximum input voltage. Use the Voc temperature coefficient to calculate:

Max panels = Inverter max voltage ÷ (Voc × (1 + β × (Tmin − 25)))

Example with Hi-MO 7 (Voc = 51.7V, β = −0.25%/°C) and a 1,000V inverter at 0°C minimum:

Adjusted Voc = 51.7 × (1 + (−0.0025 × −25)) = 51.7 × 1.0625 = 54.9V

Max panels = 1,000 ÷ 54.9 = 18 panels per string

Minimum String Length

Your string's minimum Vmpp (at hottest temperature) must exceed the inverter's minimum MPPT voltage.

Common Mistakes

• Mixing panel types in a string: Never mix different wattages or models in the same series string
• Exceeding inverter voltage: Can permanently damage the inverter and is a fire hazard
• Undersized cables for parallel strings: Parallel connections increase current — use appropriately rated cables and fuses
• No string fuses in parallel: When 3+ strings are paralleled, each string needs a fuse for fault protection

Frequently Asked Questions

Should I wire solar panels in series or parallel?

Most residential and commercial systems use series strings connected to string inverters. Series wiring raises voltage to match the inverter's MPPT range while keeping current manageable for standard cables.

What happens if one panel in a series string is shaded?

The shaded panel limits the entire string's current. Bypass diodes in each panel mitigate this by allowing current to flow around the shaded section, but output still drops. Power optimisers can solve this issue.

Can I mix old and new panels?

Not in the same string. Different panels have different Vmpp and Impp values, causing mismatch losses. Use separate strings on different MPPT inputs.