What size fuse for 100w solar panel?

If you an amateur in the electrical system, it is vital to consult an engineer. One wrong decision can ruin the entire solar panel system. I am a professional electrical engineer and have been in the field for the last seven years. 

The primary function of a fuse and circuit breaker is to protect the entire electrical system. It protects the system from heat exposure and safeguards the devices from any hazards. 

In this article, we will discuss all the nitty-gritty fuses integrated into the solar panel. 

What size fuse for 100w solar panel?

My seven years of experience suggests a 15 amp fuse is required for two 100-watt panels. One more thing I should mention, the best way to protect your solar panel system is to integrate a fuse and circuit breaker

A fuse and circuit breaker will help to safeguard the wire from getting excessively hot. We prefer to use three distinctive sections to install fuse or breakers. 

  • Within the charge controller and battery bank
  • Within the charge controller and solar panels 
  • Within the battery bank system and the inverter

I believe these three sections are an indispensable part of the solar electric system. However, it is a bit tricky to measure the size of the fuse. Hence, I prefer taking the matching of the amperage rating of the charge controller. For your convenience of understanding, I have given a table below: 

GaugeMax AmpsRecommended Fuse Size Maximum Fuse Size 
4/0 445556.25667.5

You will get two different types of the charge controller. Hence, based on the types of charge controllers, the fuse needs to be modified. For Pulse Width Modulation, I prefer to use the highest number of amps flow. Moreover, it should match the voltage of the controller as well. In this case, the fuse and wire size would be the same. 

For instance, for a 30 amps charger controller, you will need a 30 amps fuse. 

Another variety is Maximum Power Point Tracking. As the name suggests, the power drawn out from the solar panels would be higher battery voltage. It is a bit tricky to determine the size, as the produced power should be measured in the first place. 

How do you determine the size of a solar panel fuse?

The hardest part is to determine the second fuse. It is going to be used in solar panels ad charge controllers. To determine the size, firstly, I consider the number of panels installed in the system. Then I check on the following criteria:

  • Series connected 
  • Parallel connected 
  • Serially connected 

Let me explain the matter more clearly; when the panels are interconnected in the form of series, the voltage will be simultaneously added. However, the rate of amperage will remain the same. 

For instance, for four 100W panels (generating 20 volts and five amps), the entire output would be 80 volts and five amps. In the next step, you have to measure the entire amps value and multiply the numbers with an average safety value of 25%. Finally, it will culminate into the fuse size. 

Hence, the equation would be something like this:

4 panels of 100W, producing 5 amps power, therefore, generating (4 x 5 x 1.25) = 28.75 Amps. Therefore, for a structure like this, it is recommended to use a 30 amps fuse. 

Apart from the right choice of fuse, in a solar system, it is crucial to ensure the cable sizes, length of the cable, types of a circuit breaker, and fuse. 

Types of Fuse also play a crucial role in ensuring the safety of the system. Thus, it is crucial to know the different types of fuse available in the market:

  • Spade Fuse: these are basically Vehicle fuses. If you have lower amperage devices, it will work. The usual size of the fuse is around 15 amps. 
  • ANL fuses: the size ranges from 35 to 750 amps. These are cheaper and used to connect and disconnect electrical tools. 
  • Re-settable breakers: these breakers are available from 25 amps to 200 amps. If you think you have to disconnect the connections regularly, it is ideal to use Re-settable breakers. 

Why do you need to have a fuse for your 100w solar panel?

Again, I have mentioned earlier; also, those fuses are an indispensable part of the entire solar system. And the most crucial part is to integrate a fuse in the connection between the charge controller and battery because there is always a risk of overheating chances of potential failure in the system. 

No matter how well-made your wire system is, it cannot save you from overheating. If you have already installed the solar panels without a fuse, your photovoltaic system is in serious DANGER! 

Hence, the sole function of the fuse is to ensure safety and protect the electrical circuit. When the wires get overheated, the fuse gets broken. Then, it further stops the flow of current immediately. Hence, the fuse can prevent overcurrent and also ensure the safety of the electrical system. 

Where can you buy a fuse for your 100w solar panel?

Fuse is a very common part of the electrical system. No matter what size you require, fuses are easily available in all electrical hardware stores. You can simply visit a store nearby and order your required item. 

On the other hand, if you are more comfortable shopping online. Amazon has all the top brands of the fuse. For a parallel series connection, you can order a 30 amps fuse. 

Final words

You see, the fuse provides the sole function of a solar system. Moreover, it confirms the safety as well. Hence, it is always important to go for a good brand.

The price of a solar fuse ranges from $11 to $25. You can choose the top fuse brands like BougeRV, Renogy 30 A (male and female connectors with waterproof holders), PowMr, PvFarosh, Ingoulutiry, PCS Odyssey, ECO-WORTHY, and many more. 


I’m Matt, a computer and electronic embedded system developer. Currently, working as an electronic engineer. In my leisure time, I do love to blog about technology stuff. Specially, new advance high tech devices. Portable solar systems are one of topic that I love to investigate. They are becoming more powerful day by day which keep me alert.

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