“It’s a helpful way to monitor the pressure drop across the filter – it’s a good way to know when it’s the right time to change the filter because if it’s not, there’s a lot of work to do -an,” said Li. He says the average three-month replacement recommendation is based on assuming 20 percent runtime of your HVAC system (about five hours a day). Much of this depends on your climate, Li said recent study found that the median HVAC runtime in 20 homes over a year in Toronto was 10 percent, meaning those people were less likely to replace their filters.

Regarding the MERV 13 ruling, Li says that a higher flow resistance makes the HVAC fan work harder. Depending on your system, the fan can pause working as hard, reducing airflow and possibly damaging the cooling coils. However, a higher MERV rating does not equate to higher flow resistance. It depends on the quality of the filter, as Li says he’s seen MERV 13 filters have lower flow resistance than a MERV 8. Ultimately, Li says the main factor is the age of your HVAC system.

“If it’s a new system in good condition, and you’re using MERV 8 filters without a problem, then I don’t think there’s any problem using MERV 11, MERV 13, or even MERV 14 filters just because even if there is a difference in flow resistance, it’s minimal,” he said. “I think most systems can handle that, especially if you don’t change your filter all the way year.”

People with old systems should be careful, because they cannot handle high-efficiency filters. He suggests listening to the sound and feeling the flow from the cooling and heating vents in your home.

The good news is that Woosh’s smart filter can detect problems in your HVAC system. The company says it can identify early signs of coil freezing, which if left untreated can cause irreparable damage. It manages this by checking pressure drop and flow rate along with temperature and humidity levels.

Fortunately, using a MERV 13 filter doesn’t seem to cause any adverse effects on my system and I haven’t received any notifications about problems with my HVAC. My concern is that, according to the app, I still I have never had to change my filter even though it has been nine months since I installed it. My wallet is happy, but everything I’ve heard and read about the filters suggests I need to change them now.