It occurred to me that it is possible that the power consumption of the HVAC fan (in my case for the furnace + AC) may increase as the filter gets dirty. This would be very useful in terms of having an objective indicator of filter dirtiness, as I’ve been getting wildly different advice from different techs (of the same company!) about how often to replace our particle filter (which has high surface area).
Per filtration theory, the pressure drop through a filter does increase as more particles an dust deposit on it. So it is plausible that the fan would work harder (and use more power, detectable by the HS110 that I have the furnace on).
But it is also possible that the fan will use the same power all the time, and I’ll just get less air circulation as the filter gets dirty.
(The technician will change the filter in a month, so I can do the experiment then, but I was wondering if anyone knew the answer already. Our furnace is hard to access in the attic)