Can I Wire Lights in Series?

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Christmas lights, electricity projects in school, lights in old subway trains — there are several reasons you may want to wire lights in a series. Still, it is an uncommon practice with several disadvantages and safety should be the primary concern when working on anything with electricity within the home. It is recommended to always get a professional to do any work with electricity.

Lights should not be wired in series if you can avoid it. This is not a common practice in the electrical industry, and wiring lights in series may have significant safety risks. When you wire a light in a series arrangement, one fused bulb can stop the entire circuit from working. 

Keep reading to learn more about serial connections in wiring. Any type of electrical work should never be considered a DIY job with little basic knowledge of electrical work.

If you want to find the best series circuit kit, click here.

Series Wiring

When you started learning about electrical currents in middle school, the topic of series and parallel connections was likely the first subject you encountered. 

However, since most of us have long left the classroom, you probably don’t recall much about the issue, so we’ll go through a few basics first.  

A series circuit means that there is a single path that electricity uses to travel (source). This circuit is usually created with four components: a wire, a switch, a source of power (such as a battery), and the object that needs to be powered — a light or fan, for example.

Series and parallel circuits both have a current that flows through each circuit and distributes voltage (v) to electrical components.

Current is the flow of a charge, and a charge is the force created when electricity is present. The current is usually explained as the number of charges that flow through a circuit during a set amount of time (source).

Voltage is the electrical force that moves a current between two points. According to Ohm’s Law, voltage is equal to current and resistance.

A Helpful Analogy

Series circuits bear this name because they have each component connected in a row. The voltage that flows through the wire is the same in a series circuit and drops as different output components use it on the circuit.

To provide an analogy, imagine a milkman delivers 10 gallons of milk every day down a road with four houses. Each house needs 3 gallons of milk each, so while the first three will receive an adequate supply, the fourth house will not get enough. 

If the milkman distributes 2.5 gallons per household, none of them will get enough, and that is how a series circuit works — it is only as good as its power source and whether there is enough current to power all components adequately.

The series circuit is the most simple circuit in electrical wiring. As you can see from our previous analogy, it comes with a few distinct advantages and disadvantages, which we’ll get into next.  

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While there are many naysayers to series circuit usage for anything other than Christmas lights, there are advantages to using a series circuit in a few situations.

Series circuits can support more power sources, especially for smaller circuits that use batteries, allowing you to extend the usage of components.

For the average handyperson, series circuits are easy to understand and use, and they don’t require you to be a professional to create your own circuit or modify one for your specific needs. 

Series circuits are also relatively safer than parallel circuits as the chances of it overheating are minimal. This is especially advantageous if used near flammable items such as trees — another reason why Christmas lights are wired in series, as we usually expect them to stay on for longer periods.

Finally, series circuits are cheaper to install. With less complicated and expensive components, they are quite cost-effective.  


Since a series circuit sends an electrical current down a wire, it is distributed unevenly with components needing powering that are not receiving adequate amounts of charge. 

Due to the current running through one wire in a series circuit, it is not ideal for wiring traditional lighting, especially with a weaker power source. Adding lights to the system will also lead to a decrease in voltage, and all lights on the series will thus become dimmer.

A significant disadvantage is that any break in the current flow of a series circuit will cause the entire series to fail. Therefore, if an entire house’s lights are wired using a series circuit, one malfunction will cut the power source for every light in the house.

A fused bulb can cause another potential break in the system. If there is a single bulb that stops working in the series, the entirety of the system will fail until the bulb is found and replaced (source). 

Many old Christmas lights wired in a series gave owners hours of agony just to find and replace one tiny bulb amid dozens of others. Imagine having to check every lightbulb in your home every time there is a fuse issue — it’s not ideal.

When to use Series Connection

There are spaces where you can use series connections, however. An example of this is older subway cars that run on 600 volts, which is a high voltage that is not supported by ordinary, mass-produced lights. 

Since there were no bulbs that supported this voltage at one time, they use a series of 5 bulbs with a voltage of 120 each instead, and instantly there was light in the underground.

A second example is older street lights that used to be powered in series because of the ease of using longer, thinner filaments to provide power. 

For the same reason, airport runway lights still use the same system today with some adaptations, including using a transformer to continue the series in case a bulb fuses.

While, in these two cases, there are definite advantages to using series connections, it would not be ideal in a home unless you use one series connection per room.

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Parallel Wiring

When you wire something using a parallel circuit, it uses the same components as a series circuit. 

The essential difference between the two is that parallel circuits do not use one continuous wire or filament. Instead, a live wire and a neutral wire run simultaneously, and each component is connected separately to the wires running from the power source.

This is one example of parallel circuits, but there are more complicated ones that use more than two wires to control and stabilize the flow of electricity. 

To continue our milkman analogy, in this case, every time the milkman delivers milk to one house, he goes back to the farm after each stop to essentially “refill” and make sure he has enough milk for everyone.

All household and industrial wiring utilize some form of parallel wiring due to its many advantages and flexibility of use.


When using parallel wiring, components are generally more stable. So in the case of lights, if a bulb burns out or stops working, there is no effect on the circuit, and all lights continue to function as normal (source).

There is also more control of power flow, which allows lights using a parallel wiring system to turn on and off individually and even change the current flow that goes to them, allowing you to install dimmer switches.

If you introduce more lights into parallel wiring, it does not make a difference to the voltage, and all lights will continue to be as bright as they previously were.

Generally, parallel wiring is the industry standard, as it is safer and more reliable in the long run.


Since parallel wiring generally uses two lines, they require more wiring across the circuit. This additional wiring does add to the cost of the system, especially when wiring an entire house. 

The wires used for parallel systems are generally more expensive than the thinner, longer ones used in a series.

While adding to parallel wiring does not put more strain on the voltage, it does require more of the current to be utilized. 

Parallel wiring is not something that should be attempted by an amateur electrician. Because of the complexity of the system, all parallel wiring should only be installed by a licensed professional. 

When to use Parallel Connections

Parallel circuits are used in so many instances in our daily lives, with the most common being lighting. It is used in both household and industrial wiring because of the safety and reliability.

A more outward example of parallel wiring is extension cords. In this case, the extension cord serves as the power source, and every item plugged into it receives the same amount of voltage to power the component. 

Other electronics also use parallel wiring, such as home entertainment systems having multiple speakers. The speakers are connected using a parallel wiring system to allow for synchronous use throughout a space.

Since parallel circuits can support multiple components, including lights, you might be interested in how much the system can sustain. If you want to learn more about this, you can read “How Many Lights Can I Put on One Switch?” 

Parallel circuits are not restricted to indoor usage. They are used in cars, streetlights, ships, and airplanes, too. 

Consult An Electrician

An article such as this cannot cover all eventualities and codes that apply in all countries and all local municipalities.

For this reason, as well as for the safety of you, your family, and your home, it is best to consult with a local electrician before any type of electrical work.

When electricity is concerned, a little bit of knowledge can be deadly, and it is not worth taking the risk simply to save a little money.

Final Thoughts

Any type of electrical work should never be considered a DIY job with little basic knowledge of electrical work. It is always recommended to contact a professional. Parallel circuits have long been a norm in modern electricity usage due to their safety, reliability, and flexibility. While you can wire your house’s lights using series circuits, it is not the safest or most reliable manner of completing this task. 

While it has the advantage of being more cost-effective and user-friendly, the potential risks of series circuits far outweigh the benefits, especially in a residential space. The question is not whether you can use series wiring for lighting, but whether it is safe to do so.

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