Connecting Solar Panels: How To Wire In Series & Parallel Connection

A crucial point to consider for every solar installation is solar panel wiring and connecting solar panels. It is important to complete the entire circuit if you want the current to reach your appliances. 

What we mean is, once the panels are connected, they have to be connected to an inverter. Interestingly, multiple panels are connected in series, making multiple strings.

All the strings are then connected in parallel before they can be wired to the inverter. 

Fun fact: the number of strings and the number of panels depend upon the size of the solar system being installed.

It’s vital to consider how varied wire arrangements affect a solar array’s power, current, and energy so that you can choose an optimal inverter. 

Only the right inverter type can ensure the system works properly since it’s the inverter that ultimately regulates the efficiency of solar panels. 

This guide is an honest attempt at clearing all the basics about connecting solar panels so that you can understand the functioning of your solar system. Dive in for details. 

Key Electrical Terms To Know Before Wiring Solar Panels

Before understanding a solar panel connection, it is important to clearly understand the key electrical terms: Voltage, power, and current. 

Bear in mind that all these three terms are connected. Hence, the basics matter. You cannot understand the basics of wiring solar panels unless you’ve understood these terms. 

So, let’s get you started. 

1. Voltage 

Electromotive force or voltage is a term used to define the charge difference between the two points in an electrical circuit. 

The most important thing that affects the voltage while connecting solar panels is the amount of sunlight falling on the panels. The more the sunlight, the more the voltage and more energy will be produced. 

2. Electrical Current

Electrical current is nothing but the flow of charge (free electrons) in the electrical circuit. It’s measured in amps (ampere). 

3. Electric Power 

The easiest way to understand what electric power is its mathematical formula:

P = V x I. 

V is Voltage and I is Current. So, electric power is voltage multiplied by current.

In other words, power is the calculation of the rate at which the generated electric energy travels in a circuit. 

Connecting Solar Panels: Solar Panel Wiring In Series & Parallel

Wiring solar panels is also known as stringing. The way you do it determines the voltage and current that’ll be produced. The two ways of connecting solar panels are:

• The panels are connected in series 
• When there are multiple series, those series are connected in parallel 

Let’s explore both these ways in detail.

#1. Wiring solar panels in series

Connecting solar panels in series means joining the panels in a line. When the positive end of one solar panel is connected to the negative end of the other solar panel (and so on), you’re connecting them in series. It forms a string. 

The output voltage of a string is actually the collective voltage of all the connected solar panels. 

When connected in series, the current remains the same, it’s the voltage that increases. The more panels you add, the higher the voltage will be.

#2. Wiring the strings in parallel 

Connecting the strings in parallel means that the positive end of the string is wired with the positive end of another string, while both the negative ends are joined together. 

When multiple strings are connected in parallel, the voltage remains the same, and the total current is the collective current of all the strings.

As a result, if one panel or more panels in a single string are blocked by shadows, the other strings will work normally, at their maximum capacity.

How to find out the right inverter for Solar Panel Wiring?

Flashback: Do you remember what we earlier said? The efficiency of solar panels depends largely on the type of inverter you install. 

It’s time we elaborate on the topic now:

One of the jobs of a solar inverter is to maximize power generation from solar panels because the efficiency of a solar panel heavily depends on climatic conditions. 

Here are the factors you need to keep in mind when you’re choosing a solar inverter:

• How many MPPTs are present in the inverter?
• What’s the maximum input DC voltage of the inverter?
• What’s the start voltage of the inverter?
• What’s the maximum input current that the inverter can handle?

Once you know the answer to all these questions (your solar installation company will help you with the details), you’ll finally be able to understand the right inverter type that’ll be needed according to the number of solar panels you’re wiring. 

Basic Rules of Wiring Solar Panels 

• While connecting solar panels to the inverter, ensure that the input voltage does not exceed the maximum voltage level or total power. This will determine the number of solar panels connected in series in one string.
• Check that the voltage rating meets the requirements for the location in which you are installing the solar system.
• Check that the total current from all the strings connected to the inverter is less than the maximum input current of the inverter
• After confirming that your strings are of the correct length, one additional thing to consider is that all the strings should have the same parameters. It’s important because the performance of MPPTs in the solar inverter depends on the condition of the strings. 

Can More Solar Panels Be Added To The Existing Solar System?

While establishing a home solar system connection is usually ideal, start with a complete setup. A solar expert will help evaluate your power requirement and the shadow-free space available on your rooftop. Both these parameters will be used to calculate the number of solar panels you need. 

But, if for any reason you think your power consumption might increase, you must plan everything accordingly. Having a higher capacity inverter, for instance, will allow additional panels to be added in the future if needed. 

How To Choose The Best Cables For Your Solar System?

There are several factors to consider while connecting solar panels. Whilst most of them have been covered, the one topic that remains is the best wiring options. 

First things first, you will need both AC cables and DC cables. 

DC cables carry the Direct Current from each string of solar panels to the inverter. AC cables carry the Alternating Current from the inverter to the net meter or electrical load.

DC cables

• DC cables are made of copper. 4 square mm DC cables are typically used in most applications such as residential solar or housing society solar. 
• Occasionally, 6 or 10 sq mm DC cables may be used in large-scale applications such as large industrial rooftop or utility-scale solar projects. 
• Another important point to check with your solar installer is the certification of the DC cables used. 
• The cables used must be certified by EN, IEC, TUV, and UL standards so that their quality & reliability is ensured.
• Lapp, Leoni & Apar are examples of reputed & reliable manufacturers of DC cables.

AC Cables

• AC cables are used to connect the inverter to the net meter from where AC power will be distributed. 
• AC cables are available in both copper & aluminium. 
• Depending on the type of inverter, you may require 2 core cables for a single-phase inverter or 4 core cables for a three-phase inverter. 
• The size of the cable is determined by the capacity of the inverter.

Bear in mind that the longer the length of the cable, there will be more power loss. Hence, it is recommended to choose the shortest path from your solar panels to the inverter to lay the cables.

How To Protect The Wiring From Damage & Environmental Conditions?

Any wiring or cabling installed in your home is exposed to several conditions that can damage the cabling. 

For example, rodents are known to often cause damage to electrical wiring by biting the cables and damaging their insulation layer. 

As solar cables are laid on the rooftop, they are also exposed to environmental conditions like heavy rain, direct sunlight, and harmful UV radiation.

Hence, both DC and AC cables should be laid inside conduit pipes or cable trays. Conduit pipes are typically made of PVC plastic. If there are a large number of cables to be laid together, cable trays are used. 

It is important to close all the openings of the conduit pipes or cable trays with sealants to prevent the entry of insects or rodents.

Conclusion 

This article discussed how connecting solar panels determines the overall voltage and current that the solar system generates. 

We hope now you have a basic idea about what goes into wiring solar panels and how the wiring combinations are decided and sizes & types of cables are selected.  

FAQs

Q. What type of wiring is used in connecting solar panels?

Solar panels require wiring that can withstand weather fluctuations. Many solar systems use single PV wires.

Q. Is it preferable to connect solar panels in series or parallel?

Multiple solar panels are always connected in series. The strings are connected in parallel before they can be wired to the inverter. 

Q. What is the maximum number of solar panels that may be connected to my inverter?

It depends on many factors: the space on your rooftop, your power requirement, and the wattage rating of your inverter are a few.