FYI, I have given up on my delta pressure experiment because resolution of my sensor is insufficient for that use.
Use a greater delta P.
Find manual for air mover, set up instruments to read total static, supply side to return side.
Who is closing the supply registers?
Whos idea to put the piano infront of the return grill?
Inquiring minds want to know... where my mind went!
That's exactly what I started doing. Hubitat knows when my furnace is running, so I set up an app to track fan runtime.
My furnace uses big 20x25x6 filters which are pretty pricey. But after 6 months, they aren't really dirty. After I put the last one in, I set up the runtime timer.
I'd be curious to see a runtime comparison to see what is average.
Time is relative to the location. A timer can only work if it's calibrated to the location and if that location has very little change in environment. It's not logical to apply a time baseline generated in one location to another location.
I should say compare by region than...
Not really. Pets, carpet, trees, windows, kids, floor vs wall and ceiling registers, age of house, condition of ducts etc etc.
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What does pets, carpet, etc have to do with hvac fan runtime?
Doesn't impact runtime, but does impact the amount of particulates that the filter can collect. So given the exact same runtime of identical system with exactly the same flow the filter in a house with pets and carpet will have a higher delta p over the same time period than a house without pets and carpet given all other variable are the same.
In other words you cannot use hours of runtime to accurately determine the filter change interval. Accurately is the key word. Can you use a rule of thumb using hours of runtime. Sure, but it could be wrong on either side of the clean vs dirty measurement. So baselining your own house is an option. That's more or less what you are doing. You change your filter and set up a reminder. That duration for the reminder is your baseline. "Feels like 300 hours...".
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We're on two different things. 
I wasn't talking about trying to see how many hours a filter is good for. I moreso meant I was curious how much other folks fans run compared to mine.
Until I started tracking runtime, I never thought how quickly the time would accumulate.
For giggles I started the counter in June of this year. I'm just over 379hrs of runtime at 605 cycles.
You must not be in Texas.
In the summer mine runs around 500-550 hours a month. And I have a 4 ton and a 5 ton unit. Cha ching. 
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Some people run the fan 24/7/365 regardless of whether the heat or AC is running. New Systems can do this efficiently with variable speed fans. Some systems are integrated with appliances that bring in fresh air etc.
A system that is sized appropriately will not cycle often. Too much heat or too much AC causes swings and short cycles.
Then you have older homes with poor insulation or ventilation and the system runs more often...
So many variables.
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Here's an interesting monitor that uses opacity rather than pressure gradient or run time to monitor filter use. Filter Pulse HVAC Indoor Air Filter Monitor
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Weird. You could literally be blocking most of the filter with a tissue sucked into the return and not get an alert.
Dang! The electric company should be doing well!
In between HVAC and my pool my electric bill is never less than 500 bucks a month during the summer, and usually quite a bit more.
And that's with electric prices being dirt cheap in Texas at about 9 and 1/2 cents.
Just is what it is. I factored that in when I got a big house.
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Does "winter" make up for it though? I guess as long as there isn't another "once in a lifetime" freeze..
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I have 3 systems in my home. 2 are gas with AC and one is a heatpump. Any heatpump could run you more or less the same year around with some dips in the spring and fall. With gas prices more than doubling over the last few years the costs are similar with just exchanging the "fuel" type.
I'm over $500 in July and August for power in Atlanta with 3 systems.
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A 1" thick air filter is designed to have sufficient filter surface area such that they will need replacement in approximately 3 months. Unless you have a commercial HVAC unit with a huge air handler to cover 10,000+ sq feet of building area, a 6" thick filter is going to have sufficient surface area to last for many months. You might only need to replace it once a year, perhaps even less frequently. It also depends upon the quality of your air and the the MERV rating of your filter.
I replace my 1" filters every 2 months because I have two cats that generate lots of fur and dander and I use Filtrete 2200 (MERV 13) filters which clog more rapidly than filters with lower MERV rating.
