Filter Thickness

Filters that are 1-2 inches thick should be replaced every 1-2 months, while filters that are 3-5 inches thick should be replaced every 3-6 months depending how dirty/clogged it gets within the time period.

Pets

If you have pets, you should check your filter each month and replace it when its dirty. Pets release pet hair and dander into the air and they track in dirt, pollen, mold and other contaminants from outside.

Age of the Furnace:

Ideal replacement time: If your gas furnace is more than 10-15 years old, it’s probably time to start thinking about a replacement. Furnaces older than this may be much less efficient and could be prone to breakdowns.

Frequent Repairs:

If you find yourself repairing your furnace frequently, especially in the last few years, that’s a strong indicator it might be time for a new one. As the furnace gets older, repairs become more frequent and expensive.

Uneven Heating:

If some rooms in your home are much colder than others or if your furnace struggles to maintain a consistent temperature, it could indicate that the furnace is no longer operating optimally.

Strange Noises:

Unusual noises like banging, rattling, or squealing could indicate issues with the furnace, such as a malfunctioning motor or a cracked heat exchanger. These issues are often expensive to fix, so a replacement may make more sense.

Off-season (Spring or Fall):

The best time to replace your furnace is typically during the off-season, which is either early spring (after heating season) or fall (before heating season begins). During these times you may get better pricing or deals due to off-season.

Before Major Problems:

If your furnace is showing signs of failure, consider upgrading before the cold weather sets in, especially if you live in a region with long winters.