What Is Voltage Drop?

Are you looking for a more in-depth explanation of what a voltage drop is? Well, look no further because you’ve arrived at the right place.

As you may have already known, the world is a unique environment. Objects move, chemical reactions occur, and temperatures rise and fall.

The concept of energy is related to these constant actions – electrical energy included.

To be factual, electricity is a valuable and efficient kind of energy. It has become a potent instrument in the hands of numerous brilliant minds capable of creating anything from big electrical pieces of equipment to little electronic devices.

Voltage Drop Explained

What Is A Micro Inverter.

Ohm’s law states that the voltage drop across a conductor or load equals the product of current and resistance (V= I X R). This law makes up one of the fundamental concepts of electrical engineering.

In simple terms, a voltage drop occurs when the voltage at the end of a cable is lower than it was at the beginning.

Moreso, current-carrying wires have a built-in limit to current flow, known as resistance. The amount of voltage that gets missing due to resistance is voltage drop.

A garden hose is a common example for explaining voltage, current, and voltage loss. In this case, the water pressure you supply to the hose is equal to the voltage, while the water flowing via the hose is similar to the current.

The type and size of an electrical wire define its resistance, and the basic resistance of a hose is regulated by its type and size.

A circuit with an excessive voltage drop can cause lights to fluctuate or burn dimly, heaters to heat badly, and motors to operate hotter than normal and burn out.

On the other hand, any load working with less voltage than the amount needed to push its current usually works harder.

Causes of Voltage Drop

Causes of Voltage Drop

Most times, a voltage drop occurs in a circuit when there is very high resistance. The major reason for this high resistance is often because the circuit requires increased energy for powering lights or other kinds of load in the form of additional connections and components.

To understand and manage voltage drop, the supplying current, wire size, and wire length are essential factors you need to consider.

For instance, higher gauge long wires have a higher drop rate than smaller gauge wires (thicker). The reason is that a wire’s resistance is equal to its cross-sectional area over a certain distance.

The electrical resistance of a wire or cable increases when the current must travel a long distance or through a smaller cross-section. Since electricity travels a short distance, shorter cables resist the electrical current.

Moreover, lower gauge wires have a wider cross-section, which increases the surface area suitable for electrical conductivity.

Take lighting as an example. Your lights can be brighter if you are close to the power source or utility transformer.

Aside from that, extra loads or components also affect voltage drop. This is because they do not only increase distance but also increase resistance.

Above all, a circuit will produce great resistance when more sections use energy than it was created for.

Effect Of A Voltage Drop

Effect Of A Voltage Drop

Excessive voltage drop can cause issues like a slow motor, a heater that does not heat to its full limit, and dull lighting.

You can use current flow and larger cross-sectional wires with less resistance to adjust a voltage drop accordingly.

Let’s specifically look at some problems voltage drop can cause.

Motors are unable to start

Firstly, since the voltage falls below the minimum working current rating, devices that need extra in-rush current levels may not start.

Take note of MCA vs. FLA factors when creating circuits for motors.

Operation is on and off

If your device begins to work, it can go off once it detects a drop in the voltage.

This can occur during intensive operation sessions like when computers and gaming systems play “that perfect high-scoring game.”

Lighting Levels That Are Not Constant

A 5% drop in power can be visible on lighting levels. You can use street lighting design to compensate for this kind of situation.

Tripping Circuit Breakers & Blown Fuses

Since P=VI – where “P” is power, “V” is voltage, and “I” is current;

If voltage is low, you need to increase your appliance’s current for it to achieve an adequate energy level.

However, you need to note that the circuit’s safety mechanism may trip if too many loads on the circuit increase their actual capacity.

Current Consumption Increases

As a result of excessive current usage, motors and voltage regulators may overheat. The resultant effect of this overheating is that the motors and voltage regulators’ operating life may begin to shorten.

Bright lights and heaters resistant to loads will end up having shorter life spans. Besides that, fluctuating voltage levels caused by other loads on the system may cause annoying flickers.

Methods for Reducing Voltage Drops

Methods for Reducing Voltage Drops

We use various ways in power transmission and electronic design to adjust the effects of voltage drop in electrical networks.

The basic method to lessen voltage drop is increasing the diameter of the cable between the load and the source. This measure helps reduce the whole value of resistance in a circuit.

Furthermore, with high voltage usage, the energy level can be available within electricity utility. Besides, you can adjust your systems in a way that will make them work with low voltage.

Lastly, there are more advanced ways to correct high voltage drops. However, these methods will require the use of electronic parts.

Types of Voltage Drop

Types of Voltage Drop


Resistance is the voltage drop that happens in direct current circuits. Again, physical features help determine how much energy is lost and used in this case.

To give more detail on resistance as a voltage drop type, we will consider a few technical jargons.

Firstly, you must remember that a wire’s current is controlled by its cross-sectional area, length, and material class. Temperature plays a role as well.

Another fact is that the first resistor in a circuit lessens the voltage level by a huge amount. So between the DC source and the first resistor.

As a result of the main resistor’s resistance, the total energy is often lost. To make it worse, the wire that connects the first resistor to the DC source will add to the energy loss.

Meanwhile, the amount of energy used and released in the circuit will increase as the resistance increases during all of these processes.

To check the voltage loss in a direct current circuit with resistance, you’ll use Ohm’s Law. As Ohm’s law implies, the whole voltage is equal to the product of current and resistance.

Finally, Kirchoff’s circuit law says that the total of all voltage loss in all circuit parts equals the voltage supply in a direct current circuit.


Impedance is the level of energy loss inside AC current circuits. In this process of voltage drop, current flow is blocked because of resistance, which is identical to DC circuits.

However, there is Reactance in AC circuits which is another kind of resistance. Impedance combines all oppositions to current flow, such as reactance and resistance.

Fortunately, these oppositions can serve as a benefit to the community. It relies on how far apart and how big they are.

Above all, Ohm’s Law states that the product of current and impedance in DC circuits equals voltage drop.

Why We Need to Conduct Voltage Drop Analysis Study

Large changes

A voltage drop analysis study should be carried out anytime large changes are done to the electricity system.

System Efficiency

AA bigger conductor will become largely beneficial. You will end up gaining value from the way your electrical system will begin to conserve energy.

Load Protection

Minimal voltage for basic leads can cause excess heat and system failure. It can also reduce the life span of your appliances.

Damage Control

Once you follow the correct voltage drop guidelines, you won’t have to assume whether your field readings show a problem or the current is low since you prepared for the voltage drop in the model.

Operation of the System

When the voltage loss is small, some loads will still work perfectly.

Various local and national electrical codes create different rules for the current maximum drop within wirings to ensure proper electrical appliance delivery.

The voltage level drop that can be authorized ranges with each state. NEC (National Electrical Code) has a lot of laws and regulations on this issue.

It Improves Safety

NEC states all the rules and regulations that come with voltage drops plainly because the authorities want to assure the site is safe for you.

The rules explain how site owners can secure their safety and prevent punishment.

Limit Maintenance Costs

The prevention of voltage loss provides safety and compliance and saves your money on upkeep. After all, repairs and maintenance can be expensive and unforeseen problems can affect your site’s efficiency.

Furthermore, the NEC rules contain a great amount of information about regulating your electrical system while using different methods such as resistance and impedance.

Moreover, a loss in the voltage can bring an electric circuit’s whole capacity to an end.

Finally, the amount of energy that converts into a useful form of energy within the load is related to the voltage loss across an electrical load.

Managing Unsatisfactory Results

Electrical circuits in industrial, commercial, and housing projects contain many wires and connectors. Hence, the voltage loss in these systems will be important.

Furthermore, massive voltage loss can cause all of the connectors, appliances, and units connected to the circuit to operate badly.

Finally, these drops will make all the connections and wires overheat.

Prevention of Overheating

Overheating can damage an appliance that is connected to a circuit. This can put you at risk.

Additionally, it may need expensive equipment repairs and maintenance. Hence, it is essential to get the design right to manage energy loss to reduce the dangers.

Furthermore, an efficient tracking system must be in place to immediately examine any situation before it even happens.

Above all, the tracking system should come in a way that it can manage multiple electrical networks efficiently.

How To Calculate Voltage

How to Calculate Voltage

You can easily monitor voltage drop under normal working conditions. Follow these steps if you notice an excessive voltage drop in a circuit:


Firstly, one way to identify a voltage drop across a circuit part is using a voltmeter to measure the voltage drop in the circuit.

Voltmeters are made to cause little trouble to the operation of the circuit to which they are connected. They do this by reducing the current flow through the voltmeter to the minimum amount possible.

However, circuit design will be a test if this is the only method to measure voltage decrease.

Lastly, engineers can develop equations depending on the factors that make up the circuit and its loads.


When there’s a solution to these equations, you can understand all circuit voltage drops and current flows.

After that, engineers can change the model values to produce a final circuit that perfectly meets its purpose. (highest speed, lowest noise, etc.)

These equations show the connectivity of a circuit:

Kirchoff “s Voltage Law (KVL) says that the total voltage drops surrounding any single line in a circuit is zero. Conservation of energy expresses KVL equations.

Kirchoff’s Current Law (KCL) says that the sum of current flow into or out of any junction of wires in a circuit is zero. KCL equations show charge conservation.

The design of the specific circuits elements is not important. Instead, what matters is the pattern of their interconnections when writing KVL/KCL equations.

Moreover, KVL and KCL are not suitable for themselves. They often result in an equation system with more unknown values than equations.


Firstly, the device will not work perfectly if there is insufficient voltage. Therefore, each load device must receive its rated voltage for a smooth operation.

Secondly, make sure you confirm the voltage you’re going to measure is within the voltmeter’s range. Again, it may be challenging if the device is unknown.

You can always start with the longest range. When you calculate a voltage that the voltmeter can not handle, it will damage the voltmeter.

Furthermore, you may need to calculate a voltage between a specific location in the circuit or a common reference point.

Plus, link the voltmeter’s black common test probe to the circuit ground or common. Then, link the red test probe to the circuit location you want to check. Above all, you need to know the resistance of the wire you’re using to calculate the voltage drop for the cable size, length, and current

Direct Current Circuits

The cause of voltage drop in direct current circuits is resistance. For you to understand the voltage drop in a DC circuit, here’s an example:

Let’s assume you have a DC source, two connected series resistors, and a load in your circuit.

Every part of the circuit will have a resistance here. As a result, it receives and losses energy of different levels of usefulness.

Meanwhile, the basic elements determine the value of power. You will notice that the voltage across the DC supply and the first resistor is lesser than the supply voltage when you calculate it.

Plus, you can calculate how much power each one uses when you track the voltage between different resistors.

Finally, when current runs through the wire from the DC supply to the first resistor, the conductor resistance loses some of the energy the source provides.

Maintenance of Voltage Drop

Excessive voltage drop can be reduced to some extent by using a shorter and thicker wire because this brings your bulbs closer to the source and lowers the resistance of the wire.

Prevention is also possible when using a pair of secondary wires twisted together within the transformer. If the output wires are close together, you are less likely to experience unnecessary voltage drops.

You can split the output into several circuits instead of allowing the full current to send power through a single circuit.

By splitting your lights into parallel circuits, you vary the current flow through each circuit while preserving and reducing the overall drop per individual circuit.

Finally, when you follow the manufacturer’s guidelines and specifications on how to install it, you will be able to avoid problems with your light.

Conclusion on Voltage Drop

The NEC recommends a maximum voltage drop of 5% across feeders and branch circuits and 3% across the branch circuit alone.

This voltage drop level is considered to offer the right conditions for optimal equipment performance.

Note that the maximum allowable voltage drop level is not a safety measure but a performance measure.

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Finally, you may want to read other articles like this, visit our below pages.

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Akpan Iniobong
Akpan Iniobong
Akpan Iniobong is a Technical Writer for PowerVersity.com. She has a B.A in Religious Studies. She loves hiking, reading, and socializing. In PowerVersity.com, she writes buying guides and product best picks.


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