Bathroom Fans, Electrical

How Much Power Does a Bathroom Fan Use? (Explained)

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Hubert Miles

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Bathroom fans are one of the most underrated appliances that you can have in your home. You don’t realize how badly you need one until you go without one for any length of time. Bathroom fans are essential for maintaining the comfort of your bathroom, and the nice thing is that they use relatively small amounts of power. 

The average bathroom fan uses right around 36 watts of energy. Thirty-six watts also translates to 120 volts and 0.3 amps, which is the average size and power usage of most residential bathroom fans. Average power can fluctuate depending on fan features and size. 

In this article, I’ll detail the different types of bathroom fans and the amounts of power they use. Adding things like a heating element or lights will increase the power usage, but it will also increase the value of the fan. Luckily, modern bathroom fans are more efficient than they once were, which means that you’ll use less power. 

How Much Power Does a Bathroom Ventilation Fan Use?

While the average bathroom ventilation fan with a simple light fixture uses 36 watts of energy, they can use anywhere from 10 to 50 watts depending on the type of fan you purchase.

  • If you have a bathroom fan with a heater in it, your wattage use can go all the way up to the thousands depending on how long you use the heating function.
  • If, however, you only have a fan and no lights or heater, an extractor fan can use as little as 10 to 12 watts. 

The amount of power that your bathroom extractor or exhaust fan uses is mainly dependent on what kind of fan you have and whether or not it has a heater. The heater is what will quickly raise the number of watts your fan uses. Luckily, you don’t have to run the heater or lights every time you use your fan. 

A skilled electrician can hook your extractor fan up so that the heater, light, and fan components all have different control switches. You can use all three simultaneously, or you can use only one at a time. 

How Many Watts Does an Average Fan Use? 

In comparison to other types of ceiling or exhaust fans, bathroom fans use considerably less energy. Here’s a list of the different kinds of fans and the amount of watts that each one typically uses. Keep in mind that the average bathroom fan uses 36 watts of energy. 

  • Ceiling fans for kitchens, bedrooms, and living rooms – 33 watts
  • Box fans that get plugged into the wall – 100 watts 
  • Tower fans – 54 watts 
  • Table or standing fans – 40 watts 

These are the most common types of residential fans, and they all use as much or more energy than a standard bathroom fan. In the grand scheme of things, your bathroom exhaust fans are one of the cheapest things to operate in your house. 

How Much Electricity Does a Heating Unit on a Bathroom Fan Use? 

The heating unit of a bathroom fan uses up to 1500 watts to operate and run continuously. The heating unit is the most demanding and expensive component of a bathroom fan when it comes to power usage.

If you have a fan with a heater, it’s a good idea to have a separate switch or control for it, so you don’t have to run the heater every time you turn on the fan. 

Compared to a bathroom exhaust fan with light components, the heater uses nearly 100 times more electricity. Not all bathroom fans have a heater attachment, but the ones that do use much more energy on average.

You must be able to control the heating function separately from the fan and light to avoid a high energy bill and keep your bathroom comfortable. 

How Powerful is a Bathroom Fan? 

The power of a bathroom fan gets measured in CFMs or cubic feet per minute. There are many different types and sizes of bathroom fans, and you should choose the one that’s right for you. Bathroom fans are available in sizes from 50 CFMs up to 400 CFMs for larger bathrooms. If your bathroom is larger than 400 square feet, then you could need multiple fans. 

The way to calculate how many CFMs you need is by measuring the square footage of your bathroom. Every square foot should have 1 CFM of fan power. Since bathroom exhaust fans are rarely larger than 400 CFMs for residential homes, you might need two fans in a 500+ square foot bathroom. 

More fans will use more energy and electricity, but they will also keep your bathroom comfortable. Trying to ventilate a large bathroom with the wrong sized fan will result in your fan being ineffective.

Cost to Run a Bathroom Fan? 

Bathroom fans are fairly efficient overall and are not overly expensive to run in moderation. If you want to calculate exactly how much it costs to operate your bathroom fan, then I’ll explain how to do that now. 

Calculating the Cost of Running a Bathroom Fan 

Here is a step-by-step method of how to calculate the cost of your bathroom fan. 

  1. Figure out the wattage of the fan. 

Your bathroom fan or the owner’s manual that came with it should state the number of watts it uses. If you can’t find it anywhere on the fan or the manual, you can look up the type of fan you have and check Google for the answer. If that doesn’t work, you’ll have to contact the manufacturer of the fan and ask them directly. 

  1. Divide the number of watts by 1,000 to calculate the kilowatt amount. 

Once you figure out the wattage of your fan, you’ll want to divide it by 1,000 to calculate the kilowatts. Let’s say that your fan uses 100 watts. By dividing 100 by 1,000, we come up with 0.10 kilowatts, or kWh. 

  1. Multiply that number by .10. 

You need to multiply your 0.10 kWh by .10 because .10 is the national average price of electricity per kilowatt-hour, which is how the utility company calculates your monthly electric bill. If you want to be precise, you can contact your utility company and ask them what they charge per kilowatt-hour. Multiplying by .10 will get you close to the correct amount if you don’t want to. 

For this scenario, we multiply 0.10 kWh by .10 to determine the cost of running your bathroom fan per hour. The answer comes out to 0.01 kWh. 

  1. Calculate how much you use your bathroom fan. 

As a general rule, you should run your bathroom fan for 20 minutes after each shower or bath. If your family takes a total of 6 showers per day, then you should run your fan for at least 2 hours a day. That’s not counting every time you turn the fan on after using the bathroom. However, for argument’s sake, let’s say that you use your fan an average of 2 hours a day. 

  1. Multiply that number by the number of hours that you use your fan. 

You now take the 0.01 kWh of your bathroom fan and multiply it by 2 for your daily energy use, which comes out to .02. If you want to calculate your annual energy use, multiply .02, your everyday use, by 365, the number of days in the year. Your total should come out to $7.30 per year. If, for whatever reason, you decide to run your bathroom exhaust fan all day, every day, the most money you’ll spend to do so is $87.60. 

Bathroom exhaust fans don’t cost very much to operate unless you run your heater frequently in the grand scheme of things. The light feature of the fan will use nearly the same amount of energy as the fan itself, but the heater is what will cost you big bucks. 

Here is a helpful table displaying more information about what the cost of operating a bathroom fan looks like. 

Bath FanFeaturesWattsMax Annual Cost
Panasonic WhisperFit110-CFM27-watts$23.65
Panasonic WhisperWarm110-CFM & Heater1430-watts$1252.68
Broan Very Quiet80-CFM23-watts$70.08
Broan 68850-CFM108-watts$43.80
Delta BreezSignature130-CFM19-watts$16.64
Delta BreezGreenBuilder80-CFM14-watts$12.26
BV Ultra Quiet90-CFM24-watts$21.02

Should I Leave the Bathroom Fan On All Day? 

If at all possible, you shouldn’t leave your bathroom fan on all day long. Bathroom exhaust fans aren’t meant to operate all day every day, and they’ll wear out faster the more you use them.

You’ll also use much more energy than you need, which will increase your electric bill each month. Make sure to save energy and your fan by only using after showers and after using the bathroom. 

Can I Make My Bathroom Fan More Efficient? 

While bathroom fans are already reasonably efficient, there are steps you can take to increase their efficiency even more. Here are some of the best ways to make your bathroom exhaust fan more efficient. 

Install a Timer Switch on the Fan

A timer switch is a great way to make your fan more efficient and increase its lifespan. Timer switches work by automatically turning your fan off after a specified amount of time in case whoever turned it on forgets to turn it off themselves. A timer switch is handy for busy households or households with many occupants, as it’s easy to forget to turn the bathroom fan off if you weren’t the one who turned it on. 

A timer switch costs around $20 to $25 to purchase and install, which makes it a good investment down the road. Running your bathroom fan longer than it has to will increase your electric bill and also decrease the lifespan of the fan itself. 

Invest in a Fan with Moisture Sensing Capabilities

Aside from forgetting to turn the fan off, it’s just as easy to forget to turn the fan on. Fans with a moisture sensor will automatically turn on after showers or washing their hands because of the added moisture in the air. Once the fan runs long enough to lower the moisture level, it will automatically turn off without human interference or intervention. 

Clean and Maintain the Fan

Fans are like any other appliance in that they require regular cleaning and maintenance to operate correctly. As it’s being used, fans draw in moist air, including airborne particles like dust and lint. Over time, this dust and lint combo can pile up and start to clog the fan’s exhaust pipe. 

The more your fan clogs up, the less efficient it is, and you’ll have to operate it for more extended periods to remove moisture and stink from the air. By simply removing the outer cover of the fan and cleaning it periodically, you can keep your fan running efficiently and smoothly. 

In addition to causing your fan to be inefficient, clogged or dirty fans also present a fire hazard. Much like dryers, bathroom fans give off heat when they’re operating. If it gets hot enough due to being overworked, there’s a chance that the lint clogging the fan and exhaust pipe can catch fire. Take care of your fan and your home, and make sure to clean it at least once a year.  

Buy the Right Size Fan for Your Bathroom

Bathroom exhaust fans come in several different sizes because not all bathrooms are the same. The bigger the square footage of the bathroom, the bigger your exhaust fan should be. The power of a bathroom fan gets measured in CFMs, and you should have one CFM per square foot of the bathroom. 

So, for a 100 square foot bathroom, you should have a 100 CFM bathroom fan. For a 200 square foot bathroom, you should have a 200 CFM fan. Ensure a heating and cooling specialist or an electrician before purchasing your bathroom fan to ensure you’re getting the correct size.

Just remember that the bigger your fan is, the more power it will require to function. 

Do I Need a Bathroom Ventilation Fan in Every Bathroom? 

If you want to keep your bathrooms dry and comfortable, you must have at least one extractor fan in every bathroom.

For larger bathrooms, it’s a good idea to have one exhaust fan near the toilet and lav and a second exhaust fan near the shower. Exhaust or extractor fans are the only thing that will expel moisture and dirty air out of your bathroom. 

Here are some of the main ways where a bathroom extractor fan is helpful. 

Getting Rid of Moisture 

After taking a shower or washing your hands with hot water, moisture gets released into the air and condensates against the walls and ceilings. If left unattended for long periods, this can lead to mold and water damage. A bathroom fan will keep this from happening by drawing moist air through its vent pipe and to the outside of your home. 

Keeping Your Glass Surfaces Clean 

Excess moisture from hot water gets drawn to glassy surfaces such as your windows, mirror, or shower door. A bathroom fan will suck the moisture off of these surfaces and keep them clean and dry. 

Warming a Chilly Bathroom 

Bathroom fans with a heater element are great for warming up a chilly bathroom during winter. 

Providing White Noise at Night 

Some people opt to leave their bathroom fans on throughout the night to provide a source of white noise in helping them fall asleep. While many people do this, we do not recommend it. Using a bathroom vent fan for this purpose will wear out the fan motor much faster.

Purifying the Air in Your Bathroom 

With excess moisture, bathroom fans also draw dirt particles, pollen, and other microscopic things out of the air, effectively purifying it. If you struggle with allergies or asthma, a good bathroom fan will go a long way in helping you stay safe and healthy. 

Some bathroom vent fans like the Broan-NuTone AR110LKVV SurfaceShield Vital Vio Powered Exhaust Vent LED White Light & Violet Light can kill microbes yet is completely safe for humans and pets.

Help Remove Smelly Odors

It doesn’t matter who you are. Your bathroom will most likely stink after using the toilet or if it’s not cleaned regularly. The best way to get rid of the nasty smell is to turn your bathroom fan on and let it draw lingering odors out of the bathroom. 


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Hubert Miles

I've been conducting professional home inspections since 2002. I'm a licensed Home Inspector, Certified Professional Inspector (CPI), Certified Master Inspector (CMI), and FHA 203k Consultant. I started to help people better understand the home inspection process and answer questions about homeownership and home maintenance.
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