Basics of Fuses And Solar Panels

Fuses are required for solar powered setups, as they prevent damage from electrical surges and overcurrent. Fuses protect PV systems from overheating, which can cause damage and fire, especially when a solar panel is installed at home. Fuses are used in solar power systems in the same way as with other electrical setups.

Solar panels, also known as photovoltaic (PV) systems, generate energy from sunlight. There are various advantages to using such power systems. However, safety is a priority in utilizing PV systems as these are prone to electrical surges and damage. 

Read on to learn more about fuses and solar panels’ functions and safety features.  

Advantages Of Using Solar Panels

The availability of sunlight is at no cost and does not require valuable mining and fuel processing funds. Alternatively, solar panels can serve as a supplementary energy supply and aid in reducing the total cost of energy.

Power systems that utilize solar and renewable energy sources (e.g., wind and hydroelectric) can generate electricity free of cost. 

Potentially, solar energy is an excellent alternative to promoting a greener environment by replacement of fossil fuels (e.g., gas and coal) and generating electricity which essentially contributes to carbon emission and pollution.

PV Systems

A wide variety of PV systems are currently available. PV systems best suited for performance can function for an extended period and support multiple home appliances. Thermal PV systems are suitable for people who invest solely in heating energy supply.

Additionally, there are PV systems with batteries for storage which is best for people who conserve power and only use it at night. 

The diverse products of PV systems come as an excellent advantage for people as they have a wide range of choices to address their needs and requirements for power supply. 

Why Install Fuses In Solar Panels? 

Fuses installed on PV systems are commonly known as Fusible P fuses, Solar PV fuses, PV fuses, or Solar Panel fuses. 

The fuse is a safety precaution whenever there’s an electrical surge due to a high or abnormal current. The fuse ensures the electrical equipment or setup (e.g., parallel PV system and series PV system methods) safely functions.

Consequently, the fuse being a semiconductor material, melts due to the electrical surge, thereby avoiding short circuits on wirings and equipment damage. Additionally, fuses prevent fire as short circuits can cause ignite wirings and appliances at home, especially when unnoticed.

Solar Panel Fusing 

Fusing is necessary whenever you decide to generate more power. Hence, multiple solar panels or PV units must be installed and connected in parallel or series. There are differences in using which type of installation for PV systems.

Parallel PV system

The parallel setup of a PV system is where a PV unit is connected to every other unit in the circuit. It results in the voltage remaining constant, but the current accumulates. For example, setting up 5 PV units in parallel (i.e., with 12 volts and 5 amp rate per unit) would result in 12 volts and 25 amps PV system.

Series PV system

On the other hand, the series type of installation of solar panels results in voltage adding up, but the current remains constant for all units. For instance, installing 5 PV units in series (i.e., with a 12 volts and five amps rate per unit) would yield 60 volts and five amps PV system.

When To Fuse?

Diagram of standard whole house solar power equipment arrangement

Suppose the total short circuit current (i.e., amps) exceeds the maximum series fuse rating indicated on the PV unit specification sticker. In that case, you must install fuses, which are often necessary for Parallel PV systems. 

On the other hand, if the total short circuit current (i.e., amps) is less than the maximum series fuse rating indicated on the PV unit specification sticker, you may no longer need the fuses. 

Nevertheless, fuses are always recommended for circuit currents, whether less or greater than the maximum series fuse rating, to ensure safety.

Fuse Installation

The critical circuits connect the PV system, the batteries, and the connection between each electric load and the batteries.

The crucial point to install the fuse in a PV system is between the battery bank and the charge controller. You may add a fuse between the PV system and the charge controller for an extra safety setup.

Solar Charge Controllers

This item regulates the flow of electrical charge into the PV system’s battery and prevents the battery from overcharging. Specifically, the charge controller guarantees the optimum charge levels in the batteries and conservative power usage.

Consequently, the PV system would have an extended life span. 

Two Types Of Solar Charge Controllers

  • Maximum Power Point Tracking (MPPT) 
  • Pulse Width Modulation (PWM)

The key differences in variables and pros and cons between the two controllers are indicated in the table below. 

Power loss and voltage toleranceCan tolerate higher voltages.High voltage in wires pertains to lower energy lossCould not handle high voltagesLow voltage in wires can cause energy lossGenerally, a PV unit has a voltage of 12V. Hence, this controller should have a slightly higher voltage (e.g., 18V) to ensure an efficient power flow to the battery. 
Charging efficiency Convert excess volts to amps, thereby leading to optimum charge voltage and reduced time to full capacity battery charge   Unable to convert excess volts to amps pertaining to inefficient charge rate
AdvantagesExcellent capacity for PV system upgrades (e.g., the addition of PV units)Able to increase charging efficiency by 30%Able to function with high-amp PV systems up to 80 ampsHighly durable.Cheaper than MPPTAvailable in various sizesSmaller in size than MPPT
DisadvantagesLarger in size than PWMExpensive than PWMPotentially difficult to install without a good user guidePV system voltage should be similar to the battery to workApplicable only to the power of less than or equal to 60 ampsNumerous models are not categorized as safe from the Underwriters Laboratory (UL). Room for system upgrades is limited. 

Solar Batteries

Solar batteries are imperative in ensuring that PV systems run well. Additionally, as PV systems produce energy only during the day, you may not directly use the acquisition of such energy. Hence, solar batteries serve as essential power storage for PV systems and enable the use of solar energy even after sundown and during energy demand conditions or power outages.

There are different types of solar batteries, each with pros and cons, as indicated in the table below. 

Battery TypeProsCons 
Lithium-ion Longer life span (range from 3,000 to 5,000 cycles) Higher efficient power usageNo maintenanceMore storage capacityNo gas emissionSmall in size and lightEssential in cordless power (e.g., cordless air compressors and cordless impact wrenches)Most expensive relative to other battery types indicated here
GelDurableNo maintenanceHigh resistance to vibrations and shockWork well in both cold and hot temperaturesGreat life-cyclesLess prone to leakage if ever damaged VentlessSelf-discharge faster than flooded lead-acid batteriesNarrow charging profilesEasily damaged when charged incorrectly Lack ample amp-hour capacity Low charging voltageProne to accidental overchargeExpensive than flood lead-acid batteries 
Absorbent glass mat (AGM)Lower internal resistance than flood lead-acid batteriesEndure higher temperatures more than rest of the battery typesResistant to cold temperaturesLightweightDischarge slowly than rest of the battery typesLeak-proofRequire little to no ventilationPreserve static charge for long period of timeLonger lifespan than flood-lead acid batteriesUse of same charging voltageOften more suited for PV electricity systems
Flooded lead-acidAffordableRecyclableByproduction of gasNeed of ventilationBulkyCorrosiveRegular maintenance check (e.g., addition of water every     1-3 months)Should be stored upright to avoid leakage

Solar Inverters

A solar inverter is necessary for PV systems for safety at home. The inverter converts the solar panel’s direct current (DC) power into an alternate current (AC). Homes typically utilize AC for appliances and gadgets. Using DC would compromise safety as this may cause fire on appliances, gadgets, and wirings.

There are different solar inverters, and each has pros and cons, as indicated in the table below. 

Solar Inverter TypeProsCons
Standard string invertersLow cost purchaseEasy to troubleshoot problemsCheaper installationEasy to maintainSuitable for smaller PV systemLimit power production of PV systems with complex design (e.g., roof set-up, shading exposure) Potentially decrease overall power production of entire PV system when a single PV unit has low production (e.g., exposure to shade) 
Optimized string invertersConsistent power production with no drop in energy unlike from standard string invertersAid to optimize power production in complex PV system designsAllows PV unit (i.e., individlual) monitoring from entire PV system on power production dataLonger warranty benefits  Higher price than standard string invertersLabor may not be included on warrantyPower optimizers may not be repairable due to installation in factories
Micro invertersOptimisation of energy conversion at PV unit scaleSuitable for complex PV system designsAllows PV unit (i.e., individlual) monitoring from entire PV system on power production dataAllow power production to be at maximum when exposed to shadingConsistent power production with no drop in energy unlike from standard string invertersLonger warranty benefitsHigher price than standard and optimized string invertersDifficult to access for repairs as these are installed per PV unit 
Hybrid inverter systemProgrammable smart devices according to energy availability (e.g., draw power directly from the grid when available energy is cheapest or utilize stored energy when available energy from the grid is most expensive)May be used with or without a battery backup systemBest suited for complex PV system design and expansion 
Potentially reduce power efficiency relative to dedicated invertersLimited PV system design relative to micro inverters 

How Do You Size A Solar Panel Fuse?

Fuse sizes vary according to PV system setups (i.e., parallel or series types). Purchasing PV units come in different wattages (e.g., 30 Watt, 100 Watt, 175 Watt, etc.), and selecting the recommended fuse size would depend on the PV unit/s wattage.

The table below shows fuse sizes required corresponding to the PV unit/s wattage and solar charge controller. However, the examples below will no longer apply to the further addition of PV unit/s in a similar setup. Hence, consultation with an electrician is necessary when deciding to add PV unit/s eventually. 

PV Unit WattageFuse sizeCharge controller
30 Watts5A5A
100 Watts10A10A
175 Watts20A20A
200 Watts20A20A
320 Watts30A30A

Appropriate Cable To Correspond With Fuse 

Use the correct wire size (i.e., in diameter) to avoid overheating and burning and ensure safety. Specifically, whenever a cable or wire thickness is lacking concerning flowing current (i.e., amps), the heat build-up will produce a flame.

Interestingly, you can purchase an online calculator for the appropriate wire size in 

How Do You Decide Which Fuse To Choose?

It is best to always first consult with an electrician to select the proper fuse type for PV systems, especially when installing a PV unit or system for the first time.

However, you can consider these factors in choosing the correct fuse for PV systems:

  • Nominal current
  • Voltage
  • Current curves
  • Ambient temperature
  • Availability of space

Fuse rating can be located in the item’s specifications or datasheet. It is imperative to select the correct fuse that will correspond to the circuit and the power consumption of the PV system in the circuit. 


Utilizing PV systems have numerous advantages, such as readily accessible renewable energy, an eco-friendly alternative power source, reduced energy production costs, and many more. 

However, PV systems need to function to maximize energy consumption safely. The installation of fuses on PV systems significantly ensures safety by avoiding equipment damage and the risk of fire from electrical surges and overheating. 

Additionally, there should be careful and thorough considerations on the following points for safer and efficient use of PV systems: 

  • Parallel v.s. Series system design 
  • Fuse installation, fuse sizes, and suitable cables
  • Solar charge controllers
  • Solar batteries
  • Solar inverters

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