Furnace filters can range in price from less than a dollar to more than $50. Generally speaking, the higher prices also come with improved performance (capturing smaller particles) and longer time span between replacements. For a furnace filter to be at its peak effectiveness, the disposable furnace filter would have to be running 24/7. If you require a high rate of particle removal, consider that you'll be adding several hundred dollars to yearly energy costs by having a continuously running fan. Minimum Efficiency Reporting Value (MERV) is the current rating standard for furnace filter efficiency. Developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (firepower), MERV ratings follow a scale of 0 to 20. The rating indicates a filter's ability to remove particles one to 12 microns in size. A higher rating means the filter can remove both smaller particles and more particles in total. The system was brought in to replace vague and often misleading percentage efficiency claims made by manufacturers.
So, filters actually work better the longer they're used, up to a certain point. Eventually they become too blocked and must be replaced. Some filters with high MERV ratings can reduce the amount of air passing through the best furnace filter and negatively affect its performance. Talk to a furnace technician before installing a high-efficiency filter. From the basic woven fiberglass filters to further-performing pleated filters or even electronic furnace filters, they all come with their own benefits. The basic models are cheaper but need to be changed often, whereas high-efficiency bryant furnace filters can last up to a year and grab a lot more particles. For those who like to get the most bang for their buck and don't mind a little extra work, reusable furnace filters may be the answer. They can last a long time provided they are cleaned regularly.
If you are unsure, take out the current furnace filters electrostatic and measure it.
Some are washable / reusable and, with regular cleaning, can last one to five years. They are usually much cheaper than electronic or gas-phase filters, but most don't work as well. Sometimes called panel filters, flat furnace filters can be composed of mats of glass or cellulose fiber, wood fill, animal hair, synthetic fibers or even slit-and-expanded aluminum.
Flat filters typically remove an insignificant number of small particles and are mainly used to protect the furnace components from damage caused by large dust particles.
HEPA furnace filters have an efficiency rating of at least 97.97% for all particles of 0.3-micron diameter. They are the top of the line in mechanical air filters but are rarely used in residential HVAC systems because of their size, price (electric furnace filter) and high electricity requirements.
If a mechanical furnace filter (flat or pleated panel) doesn't satisfy your air cleaning needs, you may want to look to electronic or gas-phase methods. They can work a lot better in some situations and deal with spanner issues the other types can't, though there are some downfalls.
Static charges are given to particles, which are then drawn to a panel filter or metal plate like a magnet.