Impressive Way To Run the Numbers for Buying an Air Purifier

Step by Step | How Do I Run the Numbers for Buying an Air Purifier in

There’s a lot of math involved when you are looking at buying an air purifier, especially when you are going all out on your research! This page will give you every equation you will possibly need in your endeavor to make a smart purchase!

When purchasing an air purifier, you will need to calculate things like the area of your room, your annual energy cost, and the annual cost of air filter replacements. These equations may seem daunting at first, but they can be very straightforward. 

Run the Numbers for Buying an Air Purifier

This page will guide you in some step by step equations for each of the different equations you will need in your air purifier purchasing decision. We will give brief explanations for why each equation is important, and also provide you examples along the way! 


Air purifiers, like any other appliance, use electricity. And, much like every other home appliance out there, some use a lot more power than others!

Below, we have provided you with a framework to follow to find out not only how much power your air purifier uses every year, but also how much it will cost you! Electricity costs range from a few cents all the way to more than a quarter in the US for every kWh (kilowatt-hour) you use. This, in addition to how much power your air purifier uses, can really make or break the budget for you when you are looking at a particular air purifier. 

For many people, the actual cost of electricity will be negligible (generally it will be in the realm of 10 dollars a month), but for those of us who are living check to check, and need cleaner air, this can really hurt. 

Here’s the info you will need going into your equation!

Energy Consumption of your specific air purifier: 

This is Measured in Watts per Hour

(Your average HEPA air purifier will burn anything from 30 to 250 watts every hour)

Electricity Costs of your city (it’s on your electric bill): 

This is Measured in Kilowatt Hours 

(The US average cost for electricity is about 12 cents in the USA, and it is about 21 cents in New York City)

Now, find out how much electricity your unit uses every day! Here’s the equation for that:

(Energy Consumption (watts per hour)) * (Hours your unit is used) =

Here’s an example, where the equation is filled out with an air purifier that used 60 watts per hour and operates 24 hours a day. 

60 * 24 = 1,440

In this example, this air purifier will use 1,440 watts in a day.

Next, we will find out how many kilowatt-hours you will use every year with this same unit. Note that a kilowatt is 1,000 watts. 

Here’s your equation to find how many kilowatt-hours your unit uses every year:

(Previous Answer) * (Days Used Per Year) / 1,000 =

Here’s a continuation of our previous example, and we will say this unit is used every hour of every day for a whole year.

1,440 * 365 / 1,000 = 525.60

In this example, this air purifier will use 525.6 kilowatt-hours in a year.

Now, we are just about finished. All you need to do is figure out your actual energy costs. This step is pretty easy!

Here’s your equation to figure out how much running your air purifier will cost you every year:

(Previous Answer) * (Energy Cost (Dollars Per kWh))

Here’s a continuation of our previous examples. Here, we are considering that the unit is being used in New York City, where electricity is a whopping 21 cents per kWh!

525.60 * 0.21 = 110.38

Using this air purifier will cost $110.38 a year to operate! 

To find your average monthly expense, just divide this final answer by 12 (for the 12 months in a year!

Here’s a quick table that will give you an idea of how much this same air purifier will cost you to use all around the US (at the time of this article’s writing)!

PlaceMonthly ExpenseAnnual Expense
New York, New York (21 cents per kWh)$9.20$110.38
Los Angeles, California (18.6 cents per kWh)$8.15$97.76
Boston, Massachusetts (22.5 cents per kWh)$9.86$118.26
Honolulu, Hawaii (27.5 cents per kWh)$12.05$144.54
Miami, Florida (12.1 cents per kWh)$5.30$63.60
Nashville, Tennessee (10.253 cents per kWh)$4.49$53.89
Dallas, Texas (9 cents per kWh)$3.94$47.30
Seattle, Washington (11.2 cents per kWh)$4.91$58.87
Portland, Oregon (11.42 cents per kWh)$5.00$60.02
Helena, Montana (9.31 cents per kWh)$4.08$48.93
Washington D.C. (13.2 cents per kWh)$5.78$69.38
Reno, Nevada (9.65 cents per kWh)$4.23$50.72
energy cost air purifier

As you can see, the price to operate an air purifier ranges between all of the different cities across the US, but, by and large, the price is consistently below 10 dollars a month. Nowadays, that’s just the price of eating out for one person at a fast food joint! 


Before going into figuring out how much it will cost you every year to replace your air purifier’s filters, you will need two pieces of information.

How Much Does Your Filter Replacement Cost?

How Often Does Your Filter Need Replaced Every Year?

This will need to be in a year by year basis, so if your air purifier needs a new filter every three months, this will equate to 4 times a year. 

Once you’ve figured that out, all you need to do is plug it into the below equation!

(Air Filter Cost) * (Filter Replacements Per Year) =

Here’s an example of this equation filled out. We are figuring this for an air purifier that has a 15 dollar replacement filter, that needs to be replaced once every four months (Which equates to just 3 times per year).

15 * 3 = 45

In this example, this air purifier will use 45 dollars’ worth in air purifiers every year.

And that’s it! This, as we said, is a nice short equation. 

Some air purifier manufacturers really stick it to you on the replacement filters, so be vigilant. Other manufacturers make it rather difficult to find ay replacement filters, which can be troublesome. Either way, proper research can really save you money in the long run.

In order to avoid these hiccups along the road to an air purifier, it may be wise to purchase an air purifier from a “name brand” company that has been around for a while. And, as always, we recommend finding an air purifier with a pre-filter in order to get an even longer lifespan out of your main filter in order to get the most for every dollar you spend!


Air purifiers are rated for various sized rooms, and they measure this in square feet. It is important to purchase an air purifier that is rated for the size room that you are putting it in, since that is the only way you are going to really get your money’s worth. 

If you try to put an air purifier that is rated for 600 square feet in a 200 square foot room, you’ll be wasting money. Yes, the air in this room will be very clean, but an air purifier rated for a 600 square foot room is a lot costlier than one rated for just 200 square feet. Essentially, you are overbuying, and you won’t see much of any better results for doing it.

Conversely, if you purchase an air purifier that is rated for just 200 square feet and you put it in a 600 square foot room, you won’t be seeing as clean of air as you could be. This may make you feel like you are wasting money as well.

The air in this 600 square foot room will never be as clean as it could be if you purchased the correct size unit. That being said, the air will likely be cleaner in the room, it just won’t be as clean as it could be. Don’t underbuy, or else you won’t be benefiting as much as you could be!

When you are looking to calculate the size of any room in your home, you will need a basic equation from your high school geometry class, which we have below.

(Width) * (Length) =

You will have to find a tape measure to accurately measure out the square footage of your particular room. 

Here’s an example of this equation filled out for a family room that is 12 feet wide and 16 feet long.

12 * 16 = 192

This room is 192 square feet. This means that for this particular room, it would be wise to purchase an air purifier that is rated for 200 square feet.

You may be looking at our example, and be wondering why we would “overbuy” for this room, even after recommending against it just a few sentences ago. This is because of the fact that air purifier companies don’t make air purifiers for every single size room out there. After all, there are billions of different sized rooms and houses out there, and they could never make a machine for all of those. 

At the end of the day, you will probably have to “overbuy” or “underbuy” by a few square feet. No, a couple of square feet here and there likely won’t hurt you. The biggest reason why we drew a line in the sand earlier is because some people will skimp way too far, and never see the benefits of their air purifier because of it. A couple square feet of “fudged” area, on the other hand, is less likely to make an impact than a few hundred square feet. 

Recap Of Equations

These are the three main equations we find to be useful when it comes to buying air purifiers. All of them are really important when it comes to making an economical decision that can give you the cleanest air possible in your home. Never shy away from running the numbers for buying an air purifier, because (as we are sure your math teacher has said) math is your friend!

Now, if you’ve made it this far, then odds are that you’re really interested in actually getting an air purifier. If that’s the case, then I’d like to direct you to my top picks for air purifiers, all of which are great at cleaning the air, and they’re not too expensive either. On top of that, most of their replacement filters and other operating costs aren’t crazy too. These air purifiers are my favorites for a reason, after all! Once again, here’s the link to that list of air purifiers which you can check out!

Frequently Asked Questions

What Room Should I Put my Air Purifier in?

It is widely recommended to put your air purifier in your home office, living room, or bedroom. It all depends on where you spend most of your time when you are at home. After all, what would the point be in cleaning the air in your basement, if you never go down there? Just consider where you would be able to enjoy the benefits of your new air purifying unit the most!

What Are Charcoal Filters? 

Charcoal filters are one and the same as carbon filters, these phrases are used interchangeably. These filters mainly come in two different types activated and impregnated carbon. Impregnated does everything activated carbon does, but it also targets VOCs, which can be dangerous

Is it Safe to Run an Air Purifier 24/7?

Yes, in fact, most air purifiers are supposed to be run around the clock! They are safe to sleep around, and experience life around. However, ozone generators should not be used with people in the same room, as they can be hazardous to your health. 

Is it Worth it to Buy an Air Purifier?

It is very much worth it. Depending on the ailments that the air around you causes, an air purifier can actually save you money in the long run. Rather than buying medications to combat the results of breathing poor-quality air, you can clean the air itself! After buying an air purifier, you can literally come home and “take a breath of fresh air” even if you live in New York City!

Do Air Purifiers Work?

Yes, and depending on the make and model that you are considering, they work very well! Air purifiers are great for dust control, in addition to combating your seasonal allergies, which you may have thought had no fix. No, air purifiers won’t cure you of allergies, but they will seemingly cure you while you are home, since all of your allergens have been pulled out of the air. 

Where Can I Get an Air Purifier?

Air purifiers are sold worldwide, all you have to do is look online, or go to a local home improvement store or department store. We recommend looking online so you can find the largest selection of machines, and also compare prices much easier. 

How Do I Select the Best Air Purifier System?

The best air purifier for your specific needs will likely be different than someone else. The best air purifier for you will have to address what you need out of the machine! Keep in mind what it does for you (manage dust, allergens, odors), and how much you can afford!

Jonathon Silva

Jonathan Silva is our longtime Air Purifier Essentials author. He has been writing on air purification technologies for his entire professional career.

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