Author Topic: Should I replace HVAC  (Read 3858 times)


  • Magnum Stache
  • ******
  • Posts: 2848
Should I replace HVAC
« on: June 20, 2012, 02:14:18 PM »
My heater (gas) is approximately 24 years old and the AC is probably 15 years both at or near the end of their useful lives but still work just fine. 

The problem is that they are clearly not efficient even when compared to the low efficiency units available now and certainly not comparable to the high efficiency ones. 

Eventually they will have to be replaced one way or another so the question is do a I bite the bullet and get new high efficiency systems, which would require a huge cash outlay or do I continue to ride it out recognizing that whenever the HVAC is running it will cost me a bit more. 

I know someone will ask what the typical usage is and to compare rates etc. but I have only been in the house for less than a year so I don't have a history of data.

What would you do?  Have you gone from an old system to new one, if so did you see utilities decline?


  • Administrator
  • Senior Mustachian
  • *****
  • Posts: 28450
  • Age: -997
  • Location: Seattle, WA
Re: Should I replace HVAC
« Reply #1 on: June 20, 2012, 02:29:06 PM »
I know someone will ask what the typical usage is and to compare rates etc. but I have only been in the house for less than a year so I don't have a history of data.

What would you do?

Start tracking aforementioned usage and data.
I am a former teacher who accumulated a bunch of real estate, retired at 29, spent some time traveling the world full time and am now settled with three kids.
If you want to know more about me, this Business Insider profile tells the story pretty well.
I (rarely) blog at Check out the Now page to see what I'm up to currently.


  • CM*MW 2023 Attendees
  • Walrus Stache
  • *
  • Posts: 6033
  • Age: 31
  • Location: Middle West
  • Cast me away from yesterday's things
Re: Should I replace HVAC
« Reply #2 on: June 21, 2012, 06:40:11 AM »
If you live in Coastal Italy, you might not need even minimal HVAC if you're willing to acclimate. If you live on the edge of Death Valley or in the mountains of Vermont, you'll have much more significant utilities cost for one half of the year or the other. So, I guess what I'm saying is: a lot of it depends on the climate of your area whether you'll ever make your money back.


  • Magnum Stache
  • ******
  • Posts: 2848
Re: Should I replace HVAC
« Reply #3 on: June 27, 2012, 03:30:14 PM »
I have done some more work on this and it appears since September (so no real A/C season in those) I have averaged the following:

Electric - 533 KwH/month (MMM is 299/mo)

Gas - 110 therms/month (MMM wasn't specific but said heating averages 60 therms/mo in heating months of Nov-March). 

BTW my dryer is gas not electric. 

I obviously consume more than MMM, which I think is due to the following:

- My house is 60 years old and poorly insulated - I plan to add insulation in the attic but there is nothing I can do about the walls. 

- A/C and heater are old and very inefficient (point of original post).

- have a family of five so hard to contain kids in one room at any given time although they are getting better at turning lights off when they walk out.

-second fridge in garage (primary one is not that big so maybe can do without).

- lights in the kitchen, which falls into the I am too dumb to see something right in front of me category.  Almost all of our lights were CFL except about three weeks ago I looked at the ceiling in the kitchen and realized I have five, yes five, can lights on dimmer switches each with a 75W flood bulb that I am sure are on more than I want to think about but even this should move the dial dramatically.  Needless to say I went to the store that day and bought replacements.

In addition to higher usage I compared my local rates to the rates in Longmont CO where MMM - my elec rate is 3x higher and my gas is 1.6x higher - in addtion my water rate is 3x higher.  So basically if I get my usage down to MMM my monthly average will still be 2.5x higher - WTF!!!

Not sure what the cost of a high efficiency heater and A/C is but I replaced heater in my last house a few years ago for about $5k, which would equal payback of about 10 years on the heater of course it could be longer if I add insulation and keep thermostat lower than this past winter.   


  • 5 O'Clock Shadow
  • *
  • Posts: 77
  • Location: Minneapolis, MN
Re: Should I replace HVAC
« Reply #4 on: June 27, 2012, 06:31:15 PM »
If you have gas appliances OTHER than the furnace (like you stated with your dryer, how about the oven?), look at the gas usage delta between your coldest months and the warm months.  This will give you an estimate of how many therms you are using to heat.  Now, multiply this usage by you furnace efficiency (probably around 60% based on age and technology from 24 years ago), this will give the amount of gas turned to heat. Divide the amount of gas turned to heat by the efficiency of the new system and you now know your cold month usage.  Scale that # for all of your heating months (or, if available, ratio of the total heating days/year to the average heating days from your original "coldest two months" of the equation) to get your new gas usage for the year.  Multiply by the cost of a therm of gas and you now have your annual gas savings in $$$.  Lastly, do the net present value of those annual payments to determine breakeven point.

Rinse and repeat for electricity usage, but use the hot minus cold months KWH average.  This one is a little trickier as the electricity usage of other major appliances also go up in the summer because you probably don't keep your house at the same temp year round.  Also, you furnace blower with have some different inefficiencies with the new setup.

OR, you could simply wait until one of them breaks and replace them both then since it is unlikely the new units will ROI before the units fail.  :)
« Last Edit: June 27, 2012, 06:33:59 PM by bdub »