I’ve been looking into installing a fan in my bedroom recently since the only one in my home is located in the living room. Summers get quite hot here, and I don’t want to spend more on air conditioning than I need to! In my research, I found that DC ceiling fans are generally more efficient than AC ceiling fans. Naturally, I began to wonder why exactly that is.
In short, it comes down to the motor—DC motors are more effective when it comes to energy consumption than AC motors are. This is in part due to the simplicity of using an electrical current that only runs in one direction, but also thanks to the magnets used in DC motors, which enable them to use less energy. If you’re curious about how that works, read on to learn more about DC motors!
DC ceiling fans are more energy-efficient because they do not lose energy to reversing the current direction as occurs in AC fans. They also use magnet systems, which require little power to operate and which increase the rate at which the blades rotate. Energy efficiency leads to cost efficiency.
How Do DC Motors Work?
Before getting into DC motors, let’s briefly cover AC motors and how they work so that we have something to compare DC motors with.
AC stands for “alternating current,” which directly refers to the fact that the electrical current moves back and forth, or “alternates” its direction.
DC, or “direct current,” however, runs in one direction only. It has a singular, “direct” path.
Both AC and DC motors use this electrical current to produce a rotational force that, in ceiling fans, drives the fan blades to move.
Beyond the direction of the current, AC and DC motors differ in the fact that AC motors directly use their power source to operate. DC motors, however, utilize a device called a transformer to convert AC power into DC before usage.
DC motors are constructed using magnets that help drive the rotation without relying on the electrical current alone. In this way, they are able to run much more efficiently, to the tune of using 70% less energy than AC motors to produce the same result!
Average Power Consumption of DC Ceiling Fans
The power consumption of your ceiling fan depends on a number of factors, like the size of the fan and what speed it’s run at.
A DC ceiling fan running at high speeds may use around 35-40 watts, but may consume as little as 2 watts when set on its lowest speed!
In terms of money, this should only cost somewhere between $0.005 and $0.01 an hour, making running costs rather negligible.
Average Airflow Efficiency of DC Ceiling Fans
Ceiling fan airflow efficiency is communicated through “CFM/W,” or the amount of cubic feet of air moved per minute divided by the wattage used.
It’s hard to find an exact average for all DC ceiling fans, since CFM/W can differ greatly according to a number of factors.
That said, you will find that DC ceiling fans are generally more energy-efficient than AC ceiling fans.
If you’re looking for a truly energy-efficient fan, you should look for one that is 75 CFM/W or less.
DC Ceiling Fans Are Powered by Direct Current
As you might expect, DC ceiling fans are powered by motors that utilize direct current.
While it is known that DC motors are more energy-efficient than AC motors, we didn’t fully discuss why that is, so let’s get into it a bit more.
How Does Direct Current Affect Efficiency?
Technically speaking, neither AC nor DC currents are much more efficient than the other as a whole. However, they are “specialized,” or better than the other at certain tasks.
For example, AC is better for long-distance power transmission, while DC is more efficient when it comes to energy usage while running.
This is because AC motors lose energy with the constant redirection of the electrical current.
Additionally, as mentioned, DC motors utilize an additional system of magnets to help minimize the power needed to run.
DC Motors Utilize Magnets
The magnets within DC motors are used to help power the rotation of the motor’s rotor, minimizing the energy needed to maintain the production of said rotation.
How Do Magnets Affect Efficiency?
To more directly explain how the magnets within DC motors affect their efficiency, let’s look at two important parts.
First is a piece called the “stator,” a stationary part generally located on the exterior of the motor. Second is the “rotor”. This is the part that rotates and moves, and it is located inside the motor.
Both the stator and the rotor contain magnets.
When the motor is powered by a DC current, the stator creates an electromagnetic field. In turn, the push and pull of the stator’s magnets influences the rotor’s magnets to move, causing the rotor to spin.
As it takes little power to operate this system of magnets, DC motors consume less energy to perform their function. In other words, they’re more energy-efficient.
DC Ceiling Fans Offer Better Speed Control
DC ceiling fans are also able to offer better speed control and, therefore, more speed options than AC fans.
This is, of course, possible due to the way DC motors function.
Without getting into the nitty gritty, the less voltage that is used to power a DC motor, the weaker the force created, and the lower the speed. With the help of a device that is able to control the amount of voltage the motor uses, it is easy to create variable speeds for devices that use a DC motor without extra hassle.
In order to change the speed in an AC motor, a device called a variable frequency drive, or VFD, must be used. The VFD has to convert AC power into DC, change the frequency, and return the DC current to AC.
This is a more convoluted process, to say the least. While modern technology has made AC motor speed control more accessible, its complexity tends to increase the price of AC devices with speed controls, and they may need additional setup.