Is the energy cost of a BTUH consistent?
Results 1 to 7 of 7
  1. #1
    Join Date
    Oct 2001
    Posts
    63
    Except for the dehumidification advantages of a right sized AC unit, is there any operating cost advantages one way or another? In other words if the same house and air handler has a 2 1/2 ton condenser vs. a 3 or 3 1/2 ton condenser, will the electric costs be the same. The smaller unit will run longer to get the house to the desired temp but will draw less power. While the larger will get the temp there faster (although not pull as much moisture) but draw more power while it is running. This is also assuming all other factors equal including SEER, outdoor temperature, etc.

  2. #2
    Join Date
    Apr 2004
    Location
    Niantic, Illinois
    Posts
    545
    It depends on the run time variable. I would have to say yes the bigger unit would still cost more to operate. I say this based on my own home. I bought it and found the first summer the a/c didn't keep up on days above 85. I made sure the duct system was ok and wnt through the unit and made sure everything was right, it was. I ran a load calculation, the nit was 1/2 ton to small. I Replaced everything, went from an 8 seer 2 1/2 ton to a 12 seer 3 ton and my operating usage is nearly identicle. If the new unit was an 8 seer like the old one my costs would be higher now.

  3. #3
    Join Date
    Jun 2004
    Posts
    146
    Originally posted by berad
    It depends on the run time variable. I would have to say yes the bigger unit would still cost more to operate. I say this based on my own home. I bought it and found the first summer the a/c didn't keep up on days above 85. I made sure the duct system was ok and wnt through the unit and made sure everything was right, it was. I ran a load calculation, the nit was 1/2 ton to small. I Replaced everything, went from an 8 seer 2 1/2 ton to a 12 seer 3 ton and my operating usage is nearly identicle. If the new unit was an 8 seer like the old one my costs would be higher now.
    I would agree that the bigger unit would probably cost more to operate. But I'm not sure you're drawing the right conclusion about your new a/c. You said your 2 1/2 ton couldn't keep up on days above 85. Presumable your new 3 ton is keeping up. So the 3 ton is actually doing more work and producing more cooling that your 2 1/2 ton. So it's not an apples to apples comparison.

  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    To th OP,in a perfect world it would cost the same,IMHO

    What will happen in reality is,when oversized you'll turn the stat down to get some comfort,and the cost will go up.

  5. #5
    Join Date
    Jun 2004
    Posts
    146
    Even if the stat was left alone, the larger equipment would cycle more often leading to higher cycling losses.

  6. #6
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Originally posted by go_redskins
    Even if the stat was left alone, the larger equipment would cycle more often leading to higher cycling losses.

    True ,but then if the ducts leak,the lower run time would save money,due to less leakage,but then there's more airflow so more leake and infiltration,etc.,etc.,lots of variables ,in the real world.

  7. #7
    Join Date
    Apr 2004
    Location
    Niantic, Illinois
    Posts
    545
    Originally posted by go_redskins
    Originally posted by berad
    It depends on the run time variable. I would have to say yes the bigger unit would still cost more to operate. I say this based on my own home. I bought it and found the first summer the a/c didn't keep up on days above 85. I made sure the duct system was ok and wnt through the unit and made sure everything was right, it was. I ran a load calculation, the nit was 1/2 ton to small. I Replaced everything, went from an 8 seer 2 1/2 ton to a 12 seer 3 ton and my operating usage is nearly identicle. If the new unit was an 8 seer like the old one my costs would be higher now.
    I would agree that the bigger unit would probably cost more to operate. But I'm not sure you're drawing the right conclusion about your new a/c. You said your 2 1/2 ton couldn't keep up on days above 85. Presumable your new 3 ton is keeping up. So the 3 ton is actually doing more work and producing more cooling that your 2 1/2 ton. So it's not an apples to apples comparison.
    My point was a larger but more efficient unit was costing me the same to operate as a smaller less efficient unit, but if they were the same seer the 3 ton would cost me more to operate then my previous 2 1/2 ton.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event