Consumers can purchase standard-sized furnace filters from national retailers such as FiltersUSA.com, Amazon.com, The Home Depot and Lowe's, as of March 2015. Filters come in disposable and reusable varieties. Most standard filters for typical American homes are 1-inch wide.
FiltersUSA.com sells filters that fit appliances from more than 15 brands, including Trane, Carrier, Lennox and Bryant furnaces. Visitors can click on the brand of furnace they own, and then find the section labeled Standard 1" Filters to find the appropriate filter size. This website offers more than 100 different sizes of furnace filters.
Amazon.com contains more than 23,000 entries in its section labeled Furnace Filters, as of March 2015. Consumers can sort the filters by New and Popular, Price: Low to High, Price: High to Low, and Avg. Customer Review.
The Home Depot website lets customers shop for filters by depth and air quality ratings. Users can click on Shop All to find a list of every furnace filter the retailer sells. The national chain lists more than 1,200 air filters on its website.
The Lowe's website allows individuals to view the most popular filter sizes, the type of filter, and popular brands and series. The retailer offers pleated, electrostatic pleated, flat, adjustable and reusable varieties. Consumers can purchase filters in multi-packs to save money with larger purchases.
Disposable furnace filters should be changed regularly per the manufacturer's instructions. Homeowners typically remove a filter from its housing and replace it using the same size filter.