One of the things I always look at when buying a house, something I have had the pleasure of doing twice, is the heating and air conditioning units to see what their condition is like. So when I looked at this house, I noticed that the air conditioner looked to be ancient and the heater looked to have been replaced but still a couple decades old. Of course the owner said both worked in tip top shape and had no problems heating or cooling the house.
We moved in on the hottest day of the entire year as it turned out and turned the thermostat down to try and keep the place reasonably cool despite the open doors. The temperature inside immediately started climbing. When the moving trucks were gone, the air conditioner kept on running through the night and into the next day only bringing the temperature down 5 degrees in that time. Since all our stuff had been sitting in a hot moving truck all day and was a large heat sink, I figured it might take some time but on the second day, the air conditioner was still running.
Thinking it was low on freon, I called in a guy to check that which he did and said was fine but in the course of that, we found that the coils were completely plugged with several inches of grass clippings. I cleaned those off and the air conditioner functioned fine the rest of the summer. But while the heating and air conditioning guy was there, I had him inspect the rest of my system and learned some bad news. The heater was indeed over 20 years old and worse, when it had been replaced, the coils which should have been replaced at the same time hadn't been due to whomever cutting corners. So the new heater was trying to use 40 years old inefficient coils to exchange the heat. Overall, my system was found to be about 75% efficient.
Not wanting to spend lots of money on a heating system on the hottest day of the year, I let things ride for awhile. But when fall came and I kicked on the heat for the first time, the fan started up and sounded like a jet engine of a place that was taking off a runway. The system runs pretty well and has easily kept our house warm despite the 40 year old coils in the heat exchanger largely due to it being twice the size it needed to be. I could see it in my bills as they were almost as high as I normally saw in my old house in the dead of winter. To top it all off, the whole house humidifier on the side of the plenums didn't work. I found the wire controlling it cut and fixed that but it still didn't work. I traced it to the valve, the most expensive part of it, being bad. Not only that, it was ancient and didn't work well judging from all the rust I saw inside the plenums where water had run. I finally made the call and said the system needed to be replaced.
After doing some figuring, it was really a no brainer. A brand new two stage burner heating system 98% efficient would pay for itself in energy savings in about 16 months. (Note: This is after tax rebates from the government and refunds from the energy company.) A new air conditioner could pay for itself in about the same time frame. This would also include the cost of a new whole house humidifier, something my skin, throat and sinuses crave during winter. The guy said he could have the new equipment by the following week and it would take two days to complete. I said go for it.
Four weeks later, the day we ended up heading to the hospital, they showed up ready to work. I left the door unlocked and said have at it. They did their thing and did a beautiful job of the installation of both the air conditioner and the heater along with the whole house humidifier though I am still waiting on the promised new thermostat which is much better quality than my box store special and can run a two stage heater efficiently. My current thermostat can run one stage of the burners but not both. As turns out to be the norm for this outfit, they promised me they would be out on Monday to install the thermostat and here it is Wednesday before Thanksgiving and still no word of them. Fortunately I haven't paid them a cent yet so I have the upper hand. The new system works great, doesn't sound like a jet engine taking off. My throat and sinuses are whispering sweet I-love-you's to me as I speak. The only thing that remains is to see the effect on my heating bills to verify that the payback will happen as quickly as calculated.