Efficiency equals airflow.
And what hinders airflow? It is dust, which eventually becomes dirt.
Ask any professional heating or cooling technician and they will tell you stories about dirt fouling systems, causing breakdowns and creating atrocious utility bills. You see, restricted airflow causes your equipment to overwork while producing limited results.
I once had a call that the air conditioning had quit. I got to the house and saw the condenser on the outside of the house was working; the refrigerant lines were sweating which is a good thing. I went inside and put my hand over a register and hardly any cold air was coming through. I could hear the furnace fan revving like a jet engine and when I went down and pulled out the clogged filter it quieted to a soft whistle (which is normal). I went back upstairs to the register and cold air was gushing from the vent.
The woman who bore a striking resemblance to Ginger from Gilligan’s Island was so happy she ran up and kissed me (not true) but she was very happy to have the air conditioning working again.
Enough airflow prevents a furnace from overheating and a clogged filter is a major reason for a furnace breakdown. Dirty components also break down most often and even under warranty, the inconvenience of a night in a cold house should motivate us to change filters regularly.
I recommend high efficiency media filters. They are three to five inches wide and fit into a made to measure case. No dust or dirt, pollen, pet hair or dander or cigarette smoke gets past the filter. It will cost you about $120 per year to keep a clean one in place. It will cost a lot more to clean an evaporator coil or replace a heat exchanger. If you have one inch filters you should change them every other month because they get dirty quickly.
If you have an electronic, HEPA or any other powered type of air cleaner, get it maintained yearly by a qualified technician, preferably someone trained on the specific type of filter in your home. Some will require you to get involved so become acquainted with what you purchase.
Set yourself up on a preventative maintenance schedule for the furnace and air conditioner. I have a friend who says, “Maintenance doesn’t cost, it saves”.
And lastly, get your ducts cleaned, especially if you have done renovations. Drywall dust is the worst killer of furnace components and evaporator coils. Keep your filters inspected and changed during the work and your technician will thank you.
If you think of maintaining good airflow by keeping your system dust and debris free, you will save money on energy and repair costs and spare yourself inconvenient breakdowns. Keeping a clean air filter is the cheapest maintenance we know.