The best time to change your air filter is when the manufacturer recommends. However, you should also change your air filter when it is dirty. You can tell if your air filter is dirty by looking at it. If it is covered in dirt, dust, pet hair, or other debris, it is time to change the filter. If you are changing your air filters, however, it is important to choose the right one for your system and your house.

There are a lot of factors to consider when choosing the right air filter for your home. The most important factors are the type of filter and the size of the filter. Let's take a look at how to choose the correct air filter for AC in your home.

Measure your air filter.

The first step in choosing the right air filter is to locate the filter slot in your air handler. Some homes also have filters behind their return vents as well that also need to be changed. Once you locate the filters, you will need to measure them to select the accurate size. Air filter size is measured using length, width, and depth. You can use a simple tape measure to get the dimensions of your filter. Depending on the type and brand of filter, the size might already be printed on the old filter and you won't need a measurement.

If you have to measure the filter yourself, always be sure to look at the actual size before buying and round up to the next whole number to determine the nominal size.

Choose your MERV rating.

The Minimum Efficiency Reporting Value (MERV) measures the effectiveness of the air filter at capturing airborne particles.

Air filter MERV ratings use a scale of 1-20. The lower the MERV number, the less effective the filter is. As the value of the rating increases, the filter is able to capture smaller and smaller particles at a higher rate. It is important to note that filters with a higher value also restrict some airflow and could make your air conditioner less efficient.

As an example, a filter with a MERV value of four can capture less than 20 percent of large airborne particles. However, a MERV value of six means that the filter can capture up to 35 percent of large airborne particles.

Choose your filter type.

The next choice you will need to make will be the type of filter you want. Fibreglass filters are the least expensive but they offer the lowest MERV ratings. If indoor air quality is essential in your home for allergies or respiratory conditions, then a fibreglass option might not be the best solution. However, if you are focused on energy efficiency, a fibreglass filter is great because it places the least restrictions on airflow into the system.

Pleated filters are the optimal solution for moderate to high MERV ratings. Their ability to improve indoor air quality makes it tempting to buy the highest-MERV pleated filter you can find. However, if your system is not designed to work well with a reduced airflow, you risk freezing up the evaporator coil or placing a strain on your equipment. You should consider your system and equipment before purchasing a filter that restricts the flow of air.

HEPA filters have the highest MERV ratings and are commonly found in hospitals and medical settings. The majority of residential HVAC systems are not designed to accommodate the extremely restricted airflow that accompanies HEPA filters. A professional HVAC technician would need to redesign your residential system to accommodate these kinds of filters. HEPA filters are usually recommended for those most vulnerable to allergens and other airborne particles as they will capture everything from dust to viruses.

Installing a new air filter for your AC unit is an important task that should not be taken lightly. Read the manufacturer's instructions carefully before installation, and make sure you have the right tools. You should also consider the size of the filter and the area it will cover. Choose an air filter that is easy to maintain and will provide the best air quality for your home.