A Guide To Purchasing a Diffuser For A Large Room

Big living room for a large diffuser

By Mark Piatt

Updated on September 7, 2020

Can a diffuser be used in a large room?

Here at my house, we have diffusers in most of the rooms.  We do not have extremely large rooms, but the diffusers we have work fine in these rooms.  Surfing around the internet, you may see many places claiming to have diffusers for large rooms.  But do diffusers work in a large room?  I know you do not want to hear this answer, but it depends. 

Let me explain myself.  When purchasing a diffuser for a large room, there are seven main concerns:

  1. What is the capacity of the diffuser?
  2. How long does the diffuser last between refills?
  3. What is the amount of mist put out by your diffuser?
  4. What is the size of your room?
  5. How much airflow do you have in your room?
  6. What type of essential oils are you using in your diffuser?
  7. Does the diffuser look good in my space?

Let us break down each of these subjects so you can make a more informed decision when deciding on a diffuser to purchase for your large area. 

For this article, we are going to be mainly talking about ultrasonic diffusers, since this is the type that most people will be using.  The other two options would be a nebulizing diffuser and a fan-based diffuser.  I will briefly talk about these diffusers at the end of the article.


Information provided in this description is for educational purposes only.  For possible treatments of physical or mental diseases, please seek a trained and licensed health professional.  Enchanted Aromatics is not responsible for any adverse side effects resulting from the use of any suggestions, products, preparations, or procedures mentioned or from following historical uses of essential oils.

What is the capacity of your diffuser?

I thought I would tackle this subject first because it seems to be the largest misconception that sellers use to try and get you to purchase a diffuser for a large room.

When you see most advertisements for a diffuser for a large room, the one thing that becomes clear is that these diffusers have a larger water capacity and tend to be larger than a regular diffuser.

The next thing you may notice is that these diffusers tend to be more expensive compared to their smaller counterparts.

But the size of the diffuser has nothing to do with how well it will work in a large room.  The size only relates to the amount of water that your diffuser can hold.

The more water your diffuser can hold usually means the longer the diffuser will last between water refills. 

But with a larger water capacity, means you will need to add more essential oil.  The formula is usually around 5-7 drops for every 150 ml of water.  So if you purchase a diffuser with a capacity of 1800 ml, you could put up to 80 drops.  Although for the above-mentioned diffuser, SpaRoom recommends you put in 20 drops. 

The amount you use of course depends on how strong of an aroma you want and the type of essential oil you are using.

Do not get fooled into purchasing diffusers that say they are for a large room because of their capacity.  That capacity ONLY applies to the run time of the diffuser, not the size of the room it can cover. 

How long does the diffuser for a large room last between re-fills?

I love using diffusers but there is one thing I do not really like about them.  That is how often I need to re-fill them. 

Most of my diffusers usually need to be refilled about every 6 hours.  In my “busy” life, it is inconvenient and honestly, I get a little lazy about it at times.  That is because whenever I re-fill my diffusers, I usually also clean them. 

I have seen online how some people have had mold problems with their diffusers.  I have never had a mold problem.  I suspect it is because they do not clean their diffusers as often as they should.

So it makes sense to get a diffuser with the largest water capacity that can last 10+ hours right? Well no.

It has been my experience that when you use a diffuser with a large water capacity that lasts for many hours, the problem is by the end of the run time, I usually do not smell the aroma of the essential oil.

Some of that could be attributed to olfactory fatigue.  That is the inability to distinguish a smell after prolonged exposure. 

As an example, think of when you first walk into a restaurant.  You are usually bombarded with all types of wonderful (hopefully) aromas.  But after you have been sitting down for a while and enjoying the company of others, you no longer notice those good smells.  That is because your senses have become numb to the smell.

But I think the main problem is that depending on the essential oil, the lighter compounds of the oil get dispersed first.  Also, since oil floats on water, I think you initially get a good blast of the essential oil. But as time goes on, there is less and less of the essential oil remaining.

Also, essential oils are classified based on their “Note”.  This is a feature of the essential oil that distinguishes how long its scent will last.  Notes have three categories: Top, Middle, or Base notes.  The top notes last the least amount of time while the base notes last the longest.

Some essential oils even have multiple notes, which means their aroma can change while it is being used. 

Here is a table of some of the more popular essential oils showing what note category they fall under.

(Mobile users: you can scroll the table left and right)

Essential OilTopMiddleBase
Basil, HolyX
Bay LaurelX
Bergamot MintXX
Blood OrangeX
Blue CypressXX
Boronia AbsoluteX
Camphor, WhiteX
Carrot SeedX
Cedarwood, AtlasX
Chamomile, GermanX
Chamomile, RomanX
Clary SageX
Clove BudX
Eucalyptus GlobulusXX
Eucalyptus RadiataXX
Eucalyptus, LemonXX
Fir NeedleXX
Geranium, RoseX
German ChamomileX
Hemlock SpruceX
Jasmine AbsoluteX
Juniper BerryX
Lemon EucalyptusXX
Lemon Tea TreeX
Sage, ClaryX
Scotch PineX
Silver FirXX
Sweet MyrrhX
Tea TreeX
Tea Tree, LemonX
White CamphorX
White FirXX
Ylang YlangXX

What is the amount of mist put out by your diffuser?

When looking for a diffuser for a large room, this is probably the one that has the biggest effect.  A diffuser for a large room should put out a larger amount of mist than a diffuser made for a small room.

Usually, when a diffuser is advertised for being used in a large room this is the case.  That is why these diffusers have a larger water capacity.  Otherwise, you would be re-filling your diffuser every few hours – and we know that gets old very quickly.

You can gauge how much mist a diffuser puts out by dividing the number of ounces by the amount of time it lasts.  As an example, I have created a chart comparing various large diffusers along with their capacities and run times.  You can get an idea of which ones are better for large rooms by the amount of mist they put out on an hourly basis.

(Mobile users: you can scroll the table left and right)

Run Time
In Hours
Oz. /
SpaRoom MegaMist Diffuser60183.3
BlueHills Premium 200068401.7
Serene Living Fountain6.7610.7
Aromatherapy 550 ml wood grain18.5121.5
UrPower 1000 ml33.8201.7
Anjou 500 ml Cool Mist17121.4
Rocky Mountain Lux Blue Marble Diffuser5.761
Plant Therapy UltraFuse6.761.1
Pro Breeze Cool Mist128206.4
Plant Therapy AromaFuse1319.7
Rocky mountain Droplet46.7
SpaRoom TulipMist6.78.8

One thing to keep in mind though is that diffusers that put out a larger amount of mist, tend to be a little noisier compared to their lower mist models.  This is because they have larger motors.  Just keep that in mind when you are shopping for a large room diffuser.

Also, the higher output diffusers tend to be classified as a humidifier.  If you live in an area that has high humidity, this may not be something you do not want.  On the other hand, if you live in a dry area, such as the southwest United States, a high output diffuser may be exactly what you need.

What is the size of your room?

The size of your room matters.  Some people may consider a 400 sq. ft room as a large room while others may consider a 1000 sq. ft room large. 

The general rule is that the larger the room is, the less efficient a diffuser is going to be.  It does not matter what the manufacturer claims, do not expect a single diffuser to cover a 1000 sq. ft room.  For large rooms, you may even consider putting 2 diffusers in the room.

Also, if you put a diffuser in a corner, the less essential oil is going to get diffused throughout the room.  If you can, you may want to consider putting your diffuser in a more central location in the room.

How much airflow do you have in your room?

The less airflow in a room, the less the essential oil is going to get dispersed.  If there is too much airflow, the essential oil may get dispersed too much. 

Again, you may find that you need to purchase 2 or more diffusers to cover a large area. 

What type of essential oils are you using in your diffuser?

The note of the essential oil matters very much.  Essential oils are made of volatile compounds.  This means the aroma you get from the essential oil is a result of how fast these compounds evaporate.  The faster they evaporate, the shorter amount of time they last.

For example, Lemon is a top-note essential oil.  This means it evaporates more quickly than a base note essential oil such as Vetiver.  Because of this, its aroma will not last as long.  If you put a lemon essential oil in a diffuser that holds 20 hours of water, do not expect to be smelling lemon at the end of the cycle.

Also, the oil quality matters.

Many inexpensive essential oils being sold have been diluted with a carrier oil.  The scent from these oils is not as powerful and is not going to last as long compared to a quality essential oil.  Many of these inexpensive essential oils have been adulterated with other chemicals to increase profits.  These adulterated essential oils do not smell like pure essential oils and generally do not last as long.

If you have a choice of getting a 1-ounce bottle of lavender for $4.99 versus $30.00, I promise, the $30.00 bottle will smell better and will last longer. 

Do not be frugal when adding your essential oils to the diffuser.  If the diffuser calls for 25 drops and you only put 15 to save money, do not expect your diffuser to work as intended. 

When mixing essential oils, you may want to mix a top note, a middle note, and a base.  This way, the aroma will change throughout the diffusing cycle.  You can start by initially getting a blast of a top note such as lemon.  When that gets used up, then the middle note, such as cinnamon, can kick in.  And finally, in the end, you can have a base note such as Ylang Ylang kick in.

Does the diffuser for a large room look good in my space?

I know that this last one has nothing to do about how efficient the diffuser works, but let us face it, you want a diffuser that is going to match your décor, or at least, looks halfway decent. 

Along these same lines, diffusers come with many different features.  Some of these features may include lighting effects. 

For some people, the lighting does not matter, and some may not even want to have their diffusers light up.  In this case, if you purchase a diffuser with lighting effects, make sure you can turn off the light.  I know this sounds like a no-brainer, but diffusers are being sold that do not provide you the option of turning off the lighting effects.

Other Considerations

Pricing – What type of budget are you looking at?  If you are looking at options for a large room, you may be looking at purchasing 2 diffusers. 

Features – The more features the diffuser has, the more expensive it is going to be.  Also, the larger the capacity, the more expensive it is usually going to be.

Duration – How long do you want your diffuser to run between re-fills?  It can get annoying needing to re-fill a diffuser every few hours.  For the main room, it is best to get one that will last for at least 8 hours. 

Or maybe you only need one to last from the time you get home from work to the time you go to bed – perhaps 5-6 hours.  Then, in that case, you can get a smaller diffuser.

Other types of diffusers for a large room

Ultrasonic diffusers are not your only option for a large space.

Nebulizer diffusers do not use water.  They use the essential oil directly.  As a result, you get a large blast of fragrance.  For some people, this can be overwhelming. 

Another problem with this type of diffuser is it may go through an entire bottle of essential oil in a matter of hours.  This can get very expensive if you are using high-quality essential oils.

Fan diffusers usually work better in smaller spaces.  With this type of diffuser, you usually place a few drops of essential oil on a pad.  Then the fan blows air through the pad and into the room. 

Heat diffusers – these heat the essential oil to disperse the aroma.  The problem is that heat can alter the chemical composition of the essential oil.  Also, they are not very effective at dispersing the aroma in a large room.

Evaporation diffusers – this includes the popular reed diffusers.  These work by exposing the essential oil to the air and letting them evaporate naturally.  These diffusers provide a small amount of aroma in a very limited space.  Think of a desk in your office.  Definitely not appropriate for a large room.


Be aware that many essential oils may not be safe to use around infants, people with respiratory problems, or your pets.  Check out our article “Essential Oils For Odor Elimination” for more on this subject.

Final Thoughts

Using an aromatherapy diffuser for a large room is a great alternative to sprays, candles, etc.  Many of those other options contain harmful chemicals to fight nasty odors.  A diffuser on the other hand uses water, with a few drops of safe, natural oils that have very few side effects compared to the other options. 

Finding a diffuser for a large room is a viable option.  Just be aware of the limitations of using a diffuser in a large room and you should be pretty happy with the results. 

By using a diffuser along with a few drops of your favorite essential oil, you will be able to add an amazing fragrance that will improve the aroma in any large indoor space.

So have fun and enjoy the wonderful world of diffusers and essential oils.


1 thoughts on “A Guide To Purchasing a Diffuser For A Large Room

  1. turkce says:

    Having read this I believed it was extremely informative. I appreciate you spending some time and energy to put this short article together. I once again find myself spending a lot of time both reading and commenting. But so what, it was still worth it! Madalena Reeve

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