Solar Voltage Drop Calculator (Everything You Need to Know) -
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Solar Voltage Drop Calculator

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Understanding voltage drop is crucial for maintaining the efficiency of solar power systems. Voltage drop occurs due to resistance in the wires, causing a small loss of electrical current as it flows. This can reduce the effectiveness of solar panels over time. Calculating voltage drop involves using the formula: Voltage Drop = 2 x L x I x R / 1,000, where L is the cable length in meters, I is the current, and R is the resistance per kilometer.

Key factors affecting voltage drop include wire material (copper is better than aluminum), wire size (thicker wires have less drop), and wire length (shorter wires reduce drop). The current flow also impacts voltage drop, with higher currents increasing the drop. By understanding these factors and using available datasheets, solar system owners can minimize voltage drop and maintain system efficiency. For those needing help, Shop Solar Kits offers customer support for solar queries. This knowledge ensures solar panel systems remain productive and efficient, maximizing the benefits of solar energy.


A common difficulty in solar power maintenance is understanding and calculating voltage drop and the effects it has on your overall system.

There are loads of solar calculators available online from sun-hours calculators to even solar lease calculators so you can figure out whether a solar system is right for you. But one that’s often overlooked is voltage drop calculators.

Often solar voltage drop calculations are overcomplicated and difficult to comprehend, especially for solar newbies. Thankfully, these calculations are easy to understand and don’t require intensive maths to complete.

Utilizing sustainable solar energy to power your home is among the most informed green energy choices you can make.

Solar panel systems allow individuals worldwide to power their homes with clean energy, freeing them from dependence on centralized power systems.

Making the switch is straightforward but understanding accurate solar calculations and the intricacies involved in solar maintenance can be an arduous task.

So, let’s explain what voltage drop is before you decide to purchase a new solar panel for your home or RV.

What Is Voltage Drop

Voltage drop is common in all solar panel systems and it's something that you should be on the lookout for if you notice a decrease in efficiency. However, before we get into the nitty-gritty of it, let’s explain what voltage drop is.

In all electrical circuits, the current is continuously flowing, but during circuit flow, a tiny amount of voltage is lost. The electrical current that is lost is largely due to the wire resistance between your deep-cycle solar battery. This mechanism of loss is commonly known as voltage drop.

how to calculate solar voltage drop

The wire carrying the current gets warmer because of the electrical flow and due to the increase in heat, the voltage decreases from one end of the wire to the next. The difference in resistance between these two points is described as “voltage drop.”

This is because of one of the most important equations in electrical engineering: Ohm’s law. This is commonly written as V=IR (Voltage = Current x Resistance).

While this is a normal process, prolonged voltage drop can lead to your solar panels becoming significantly less productive and efficient in converting the sun’s rays into storable energy.

Solar Voltage Drop Equation

There is one simple equation that you can use to work out the voltage drop in your solar panel system.

The first one is generally the one used to determine the decrease in electrical potential for solar panel PV cables. It is often used in conjunction with a PV solar calculator.

The equation is as follows:

Voltage Drop = 2 x L x I x R/1,000

The 2 in the equation refers to the round trip in a single cable. The ‘L’ refers to the length of the cable in meters. The ‘I’ refers to the ampacity or the current flowing through the wire, and the ‘R’ refers to the resistance per kilometer.

All the units of measurement for these calculations must be written in metric.

Dividing by 1,000 ensures that the final answer is converted to kilometers instead of meters. Most of these metrics you can find on the cable datasheet.

Let’s say we have an L value of 25 meters, an I value of 20, and an R-value of 8.286.

(2 x 25 x 20 8.286) / 1,000

All we would have to do is put those metrics into the equation and we get the voltage drop, which in our case equates to 8.286 energy loss.

Thankfully, solar panel owners can minimize voltage drops to ensure that their system is functioning at the highest efficiency.

There are a few things that you need to work out for the voltage drop in your system. This is the initial step before trying to minimize the voltage loss.

Wire Material

solar voltage drop calculation

One of the most important components of calculating voltage drop is the material of your wires. The two most commonly used wire materials are aluminum and copper.

Copper is a much better electrical conductor than aluminum, which in turn causes it to have a lower voltage drop.

Wire Size

In addition to wire material, wire size plays a significant role in voltage drop. The thicker the wire, the less energy loss. The thicker the wire, the more space there is for the flow of electrons to move without bumping into each other.

Wires with greater diameters are less prone to significant voltage loss, while thinner-diameter wires experience greater levels of voltage drop. If you’re unsure of your wire size, you can find a cable data sheet online that has the wire details you need to carry out voltage drop calculations.

Wire length also affects voltage drop. Shorter wires connected to your solar panel system will have lower voltage drop levels than longer wires. This is because in short wires their current doesn’t have to travel as far, so the chances of losing energy within the system decrease.

Flowing Current

Lastly to determine voltage drop you would need to determine the current flowing through the wires at a given time.

solar voltage drop chart

An increase in current flowing through the wires of your system will result in an increased voltage drop rating.

The common name given to current carrying capacity is known as ampacity, which is the maximum number of electrons that can be pushed through the wire at the same time.

You can find the ampacity on your cable datasheet. Once you have all these metrics you will be able to work out the voltage drops of your system using a simple equation.


As you can see, solar calculations don’t have to be complicated and they often only require a few metrics that can be found on a datasheet.

Once you have all the necessary variables you will be able to calculate the voltage drop using the simple equation given.

If you require any additional assistance regarding any solar then you can always contact Shop Solar Kits. We have exceptional customer care and won’t hesitate to assist you with your solar queries.

Now that you’re an expert in voltage loss calculations you can go ahead and work out the voltage drop of your solar panel system. Additionally, you can become a master of all calculations and try your hand at an optimal solar angular calculator.

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