A number of different types of filters are for sale today, but these discount filters provide a high-quality and economical alternative to some of the more expensive brands. You can take your pick among several different models in the 18x24x1" size. Regardless of which filter you select, be sure to check it for dirt and clogs often.

The standard fiberglass filters are inexpensive. They may come in blue or white and should be changed monthly. They do a good job of removing large particles from the HVAC system. They are easy to install and remove. They are MERV 4 rated.

The pleated filters produce much higher indoor air quality. The accordion-like pleats on these discount filters are optimally spaced and electrostatically charged to increase efficiency. This also reduces air flow resistance, which lowers the strain on the HVAC unit and may even increase its life. These generic filters can be used in both residential and commercial systems. Three different ratings are available: MERV 8, MERV 11 and MERV 13. The higher the rating a filter has, the better it performs. A minimum of MERV 8 is recommended for those attempting to meet LEED standards. They are easily installed and will last for a full three months.