Buying a Cheap Air Purifier


In this guide we’ll show you how to determine the best value air purifier for your specific application. We’ll end this guide by showing you what is currently the best low cost option on the market.

Value Analysis

We find it’s helpful to break down any value analysis for an air purifier into two different categories:

  • initial cost
  • long term cost

Initial cost

Initial cost involves

1. the price of the air purifier

This is easy. Is the air purifier cheap or expensive? If it’s extremely cheap this certainly makes it an attractive option and a good candidate for having good value. If it’s extremely expensive, it may be outside your budget but more importantly, it needs to offer quite a bit for it to be a good value.

Top rated units fall in the $120 to $200 range. We generally do not recommend units that cost less than $100 (If you find this price range unaffordable we recommend that you hold off on your purchase - it’s that important).

More expensive units are also not recommended. Not because of their high price but because they don’t offer enough at that high price.

2. what you get for that price – most filter type and CADR or CFM per $ ratio

Yes, the air purifier you’re buying may be cheap or it may be expensive but what do you get for the price?

The two most important “features” to look out for are

HEPA or not

This is easy. Does the air purifier come equipped with a HEPA filter? If yes, then it’s an option. If no, then it’s not an option.


This is the output of the air purifier. The higher the CADR or CFM the greater the output. Generally, the higher the price, the greater the output – but not always – so watch out and definitely read this before you buy.

All top rated units have HEPA filters and a great CFM/$ ratio.

Long term cost

Long term cost gets a little more complicated.

Here we have to take into account

  • Energy costs
  • Filter replacement costs

1. energy costs

The good news here is that energy costs can be extremely low, if you buy the right model.

In our general buyer’s guide, we get into detail as to why we recommend 250 CFM units over any other size air purifier on the market. We make this recommendation for many reasons but one of the primary reasons is this:

250 CFM units can be run on a lower fan speed that provides sufficient CFM

  • to lower and maintain particle concentration in small rooms
  • to maintain particle concentration in large rooms

At these lower fan speeds these units draw less than 10 watts of power. That equates to only $10 per year in energy cost even if you run them 24/7, 365 days of the year.

Of course, if you’re using such a unit in a larger space you will have to set it to its maximum fan speed to initially lower room particle concentration. But you don’t have to run it on this speed all the time and even when you do the power draw is still very reasonable at around 60 to 70 watts.

Top rated units have about 250 cfm of output and because of that are able to have great energy efficiency in many different applications. Those units that do not have low energy efficiency scores in their respective reviews.

2. filter replacement costs

Filter replacement can be expensive. We made sure to select top rated units with reasonable filter replacement costs but that’s not to say that there aren’t models on the market that have rather unreasonable filter replacement costs.

Here’s what you should look out for when assessing a unit’s filter costs.

1. Manufacturer Recommendations About Filter Replacement Frequency

Don’t use them! Manufacturer recommendations vary wildly between different models because there is no industry standard recommendation to make.

Yes, it could be argued that different models have different pre-filters, different design, etc. which can contribute to different filter replacement windows.

However, our testing has shown that replacement frequency much more depends on

  • how often you run the air purifier
  • what speed you run the air purifier on
  • the particle concentration of the air you’re purifying

If the air you’re cleaning is extremely dirty, the filter will “saturate” faster and will need to be replaced faster. This is no fault of the air purifier. In fact, the quicker the filter saturates the better the air purifier is working – the cleaner it’s keeping your air.

How can a manufacturer know any of these variables, especially the last one? This is why we standardize how filter cost analysis in the following way:

We estimate that you’ll only need to replace the unit’s HEPA filter once per year in reasonably clean air. We then compare all units on the market according to this requirement.

This presents something important to watch out for:

2. Hidden Carbon Filter Costs

Most air purifiers on the market come equipped with a HEPA filter (for particle removal) and a carbon filter (for gas removal).

Carbon filters, for the most part, need to be replaced much more frequently. This is because

  • They’re usually very thin
  • Often they act as a prefilter that has to be thrown away and cannot be washed
  • They adsorb chemical gases and saturate much faster than HEPA filters do with particles

We estimate that you’ll need to replace the average carbon filter at least 2x per year* – compared to 1x per year for a HEPA filter.

HEPA filters and carbon filters are often sold as a combo pack – meaning you buy them together and not individually. Many manufacturers do not sell them individually at all.

Here’s the problem:

Many manufacturers bundle only 1 carbon filter with 1 HEPA filter. This means that you have to buy multiple combo packs to keep up with the very reasonable 2 times per year carbon filter replacement schedule we estimated above.

This means that you’re now buying multiple combo packs per year even though you may only need one HEPA filter per year.

*Note: This is actually a low estimate. You’ll likely want to replace it at least 4x per year. We just use the lower estimate because a higher estimate would make filter replacement costs even more unreasonable for many models on the market.

The small air purifier, small air filter, small filter cost trap

Smaller air purifiers have smaller cheaper air filters.

It’s unreasonable to compare the filter cost of a small unit to that of a large unit. Here’s why.

There’s only so many particles in a room that need to be filtered by the air purifier’s HEPA filter. As these particles are filtered they begin “saturating” the filter.

Assuming the same amount of particles, (and the same output – you can set a large unit to approx. the same output of a small unit by setting it to a lower fan speed. In any case, assuming the same amount of particles and output,) a smaller filter will saturate much quicker than a larger filter. Why? Because the smaller filter has less surface area to saturate.

For example, if filter A has a surface area of 100 sq. in. while filter B has a surface area of 200 sq. in. filter A will saturate twice as fast. If filter A is $5 and filter B is $10, replacement cost is equal because you need to buy two of filter A to remove the same amount of particles as filter B (which will saturate in double the amount of time).

In the example above, filter A is a good example of a filter for a small air purifier while filter B is a good example of a filter for a large air purifier.

The bottomline here is that filter costs for small and large air purifiers are much more similar than they appear at face value. All other factors being equal, filters for small air purifiers are usually not any less expensive than filters for large air purifiers.

Use a meter

The 1x per year HEPA replacement schedule we talked about earlier is an estimate. To truly maximize how long you can use any particular HEPA filter use a particle meter.

Use it at the beginning of the filter’s life to see how low the particle concentration gets in the room and on what setting.

Use it again when you think it’s getting close to the end of the filter’s life. If the particle concentration is still getting just as low on the same settings there’s no need to replace the filter.

We’re going to wrap things up by giving you an example of a top rated unit that does well in the value analysis we just described – in other words, we’re going to show you a unit that is just a very good value all the way around.

Best Cheapest Air Purifier

The best least expensive air purifier currently on the market is the Winix 5500-2.

This unit retails for a very reasonable price – so a very reasonable initial price.

But more importantly, it’s a great price for what it offers: First of all - 250 CFM. There’s really no other model on the market , at least at this time, that offers this much CFM for this price. So you’re getting a great CFM/$ ratio with this unit.

It also has a pellet based carbon filter for gas filtration – better than fiber coated. It has a HEPA filter – remember, you absolutely want a HEPA filter.

In terms of long cost this unit does very well also. Filter replacement costs are very reasonable.

The unit’s carbon filter is also washable which greatly extends the life of the filter. Not to mention the pre-filter which extends the life of both the carbon and HEPA filter. This unit also has superb energy efficiency.

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