Which furnace filter should you buy
One of the easiest ways to keep the furnace repair company (us!) from needing to visit your home is to consistently replace your furnace filter.
Furnace filters are rated on what’s called the minimum efficiency reporting value (MERV) scale. The scale goes from 1 to 20, with most residential filters in the 4 to 12 range.
The lower the MERV rating, generally the less expensive the filter.
A filter with a lower MERV rating will filter fewer particles out of the air than a higher-rated filter. But higher-rated filters limit air flow – especially as they catch more dust and other particles. So the higher-rated filters may reduce the effectiveness of your furnace (causing it to work harder to heat your house).
According to familyhandyman.com, a MERV rating in the 7 to 8 range is a good balance between cost and efficiency for most home owners.
You should inspect those filters each month and likely change them every three months. If you have cats or smoke, you might need to change filters more often.
Washable filters are also available. You wash them each month and put them back in.