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  1. #1
    Join Date
    May 2013
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    ROI of a 2 stage vs single stage

    Hi,

    I'm about to replace my 5 ton system and am contemplating a 2 stage vs single stage (both would have a variable air speed handler). I've done the research and understand the comfort benefits. Those alone can't justify the cost for me because I have a single stage already and am not bothered by it. However many articles state that 2 stage has lower utility costs. Are there any figured for ROI (return on investment)? For instance, how much does one save in electricity by upgrading to a 2 stage over a single stage (same make, just one level up). One popular one has been Bryant Legacy vs Bryant Preferred. Are we talking $30 a year or $333 a year? Wondering how long the upgrade will take to pay for itself, if ever.

    Thanks

  2. #2
    Join Date
    Jan 2014
    Location
    New England
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    Why don’t you do a load calculation 1st, that alone may tell you that you may get by with a smaller unit.

    Here’s a free one: http://www.loadcalc.net/

    I suppose to a degree the voltage to your residence affects amperage draw.

    The Legacy vs the Preferred may use the same compressor as an example, but have less standard features than the Preferred, such as it shows an exposed OD coil on the Legacy, whereas the Preferred has a full wrap around metal louvered skin to help protect the coil. The Legacy is bare bones, probably no safety pressure controls. Outdoor unit in the sun vs shade dirty OD coil vs squeaky clean coils, all those things raises refrigerant pressures which means the compressor works harder which means your amperage goes up..

  3. #3
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Quote Originally Posted by Bazooka Joey View Post
    Why don’t you do a load calculation 1st, that alone may tell you that you may get by with a smaller unit.
    Agreed

    Finding out a smaller unit will cool the house is your best ROI !

  4. #4
    Join Date
    May 2013
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    Thread Starter
    Thanks for the responses.

    I got 3 quotes and all said that my existing 5 ton was sized right. One said too big at first but then after going through the house said it was right. It's 3500 sq ft of cooling space with many large windows, 2 story ceilings, skylights, etc. I've done a heat loss calc because I'm also replacing my boiler. I'll update the temps and get a load calc.

    But putting that aside for the moment, because whether I'm 3 ton or 5 ton I still have the same q...roi of single vs 2 stage. Is there any data that shows yearly savings for that?

    Thanks!

  5. #5
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
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    Two stage ac is more efficient in 1st stage(70% capacity) than second stage but is kind of a wash as it runs longer. Your getting more savings due to 2 stage systems usually being offered at 16-17 seer ratings. But even a 2 stage 5 ton is probably going to top out at 15 seer. You’ll save more money over the life of the equipment if you can drop the size down to 3.5-4 tons. 5 ton systems almost never have enough ducting and are usually only delivering 4 tons of cooling inside the home, yet your paying to run a 5 ton=lost $$

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    I'd say ROI on 2 stage over single stage at same SEER level is zilch. Even diff between a couple SEER points is minor. And also if you are looking at heat pumps, look at HSPF, the SEER of heat mode. I've seen some really high SEER heat pumps that rate at the bare minimum 7.7 HSPF.

  7. #7
    Join Date
    May 2013
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    Thread Starter
    Perfect, thanks! Exactly what I wanted to know

    Side question since it came up here. I did a heat loss calc with the Slant fin app. Since it's all the same data (room size, glass, door, etc) could I just change the outdoor and indoor temps and use it to get the load calc mentioned here? Or is a different algorithm?

    Thanks again!

  8. #8
    Join Date
    Jul 2010
    Location
    nebraska
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    Quote Originally Posted by MSmithHT View Post
    Perfect, thanks! Exactly what I wanted to know

    Side question since it came up here. I did a heat loss calc with the Slant fin app. Since it's all the same data (room size, glass, door, etc) could I just change the outdoor and indoor temps and use it to get the load calc mentioned here? Or is a different algorithm?

    Thanks again!
    Probably won't work for cooling. Heating load is just temperature change. Cooling is temperature and moisture.

  9. #9
    Join Date
    May 2013
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    Thread Starter
    Ok thanks!

  10. #10
    Join Date
    Nov 2004
    Location
    SW FL
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    Quote Originally Posted by MSmithHT View Post
    Hi,

    I'm about to replace my 5 ton system and am contemplating a 2 stage vs single stage (both would have a variable air speed handler). I've done the research and understand the comfort benefits.

    Those alone can't justify the cost for me because I have a single stage already and am not bothered by it. However many articles state that 2 stage has lower utility costs.

    Are there any figured for ROI (return on investment)? For instance, how much does one save in electricity by upgrading to a 2 stage over a single stage (same make, just one level up).

    One popular one has been Bryant Legacy vs Bryant Preferred. Are we talking $30 a year or $333 a year? Wondering how long the upgrade will take to pay for itself, if ever.

    Thanks
    ZIP _ _ _ _ _
    _____ North of 42'N Latitude or SOUTH of 31'N

    Windows __ 400 or 800 Sq Feet Glass Area
    SHGC 0.2 or 0.6
    U-factor 0.2 or 0.9

    3,500 Sq Feet, 2-story
    __ _ _ _ ... Years old -_ Built 1980 or 2010

    Infiltration: ??? 0._ _ A.C.H. Natural per Blower Door Test

    My 2-stage A/C system runs > 12 hours per day in Low (70%) Stage.
    ODT > 91'F, 2nd stage
    No heating is required.

    I am not aware of a 2-stage unit being MORE EFFICIENT on low stage.
    … Probably in the Ball Park of 72% power for 70% of full capacity
    $0.10 or $0.40 / kw-hr ????
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  11. #11
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
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    I was able to find Trane paperwork that showed the EER and SEER of stage 1 vs stage 2, although I couldn’t find the same for Carrier

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