Dear PoPville – Roof a/c replacement?

Photo by PoPville flickr user AWard Tour

“Dear PoPville,

I have a question about central a/c. We have a system but it is 20 years old and needs to be replaced. The ductwork is fine but the compressor and other mechanical elements are on the roof. Has anyone had this done? How much did it cost? Thanks.”

36 Comment

  • No one is going to be able to answer this question. Rather than waiting around for a bunch of subjective and ultimately incorrect answers, why don’t you just call a few HVAC folks to come by and give you an estimate.

    You are really asking two questions.

    A. How much to replace my outdoor A/C unit. None of us knows because we have no idea the tonnage it currently is, how efficient you want to go. The price differential between those two things along could be ~7K.

    B. How much to get it on the roof. While they won’t break that price out, they will charge you more to get the quipment to the roof rather than it sitting on the ground next to your house.

    Seriously, just call up a few people. They would probably be out there tomorrow and can give you a decent estimate right there.

  • I don’t see what’s wrong with someone asking this question. Sure, this particular homeowner won’t know for sure until he/she gets estimates from HVAC people, but it doesn’t hurt to ask other homeowners how much it cost them.

    Sheesh. What is it with posters criticizing other posters for having the temerity to ask about topic XYZ??

    • Agreed. I’d be interested to know how much this is, even though I’m not in the A/C unit market right now. I’m sure not going to price a unit out just for shits.

      I find these posts the most helpful on PoP. It’s the “should I get braces” emails and the emails/posts that unnecessarily scare people that deserve scorn, and not the home improvement emails.

    • Because there is zero point unless we also know the extreme basics like “How large is your house”, or What is the tonnage of your current A/C system”?

      It’s like asking someone what it cost to get a new car, without stating whether they wanted to get a 2 door Honda, or a Aston Martin. No one can answer the question.

      I mean, the answer to this question is anywhere between ~3K and 20K. How is that remotely helpful to anyone?

      • Thanks for your opinion, you’ve adequately expressed it twice now. Maybe for the duration of this post, you could refrain from repeating yourself again…

      • Well now the OP knows, based on the A/C expert, that it will be more than $3K or less than $20K.

        That is really helpful info…

        • That is exactly A/C’s point! Without any specifics on the project, any numbers people could throw out would be so general and widely varied as to be useless.

          I provided my example (below) but I have no idea if my stats match the OP’s, so who knows if it’s of any use. I sure don’t.

          • I’m almost always pro-sarcasm, as well as pro-indignation, but I wish we’d debate the usefulness of a variety of posts other than the home improvement ones.

          • Fair enough. The question *could* have been more concise, but [sigh] who’s got the energy sometimes, y’know?

            I don’t have a dog in this hunt.

  • I was in this situation where the contractors thought they could get the unit to the roof by hand, but ended up having to call a crane last minute. The invoice for the crane was about $700.

    • Should have been more specific here. I believe the total cost was around $3500. I’m sorry, can’t remember the size of the unit.

  • I have a mid-street no access row house that uses two zones. I just replaced one of the two roof units with a 1&1/2 ton carrier compressor (no air handler in this charge). Duct work needed cleaning, crane, etc…total was $8K

  • pablo .raw

    Also, you should find out about the size (tons) of your current equipment and its efficiency. The units that are sold these days are obviously more efficient than the ones 20 years ago (I think you should be looking for at least 13 SEER) but the size should be the same or maybe even smaller (if the older equipment was sized properly and was taking care of humidity and heat). Be careful with a contractor offering you a bigger unit than the one you have, in AC terms, sometimes bigger is not better.

  • I don’t know about getting it on the roof, but in general, cost for the system can range widely, as A/C said.

    Although I agree you might have done better to ask for AC contractor recommendations here, I’ll shoot out a number based on our (currently reviewing quotes) experience:

    2.5 ton system
    16 SEER efficiency
    Brand name: Payne (manufactured by Carrier)
    unit on the ground, not the roof.
    roughly 1600 sq.ft. living space

    roughly $10K.

    • pablo .raw

      There are so many things that could influence the size of the unit (type of windows, doors, air leakage of the house, walls, orientation, insulation, etc.) but for a project of similar size as yours (1600 sq. ft.) I calculated 2 tons 10 SEER (2006). The contractor asked to make it 2.5 tons, since it was the top 2 floors of a 4 story rowhouse.

    • I work in the HVAC industry, and I’m a regular PoP poster, but I’ll keep it Anon for this to keep personal and professional opinion separate.

      That being said, Payne is not Carrier. Anyone telling you so is not being completely honest. They’re manufactured by the same Mega Conglomerate, but there’s a big difference in product. Also, 10k for a 2.5 ton Payne system seems awfully steep assuming it doesn’t include major duct modifications.

      • Hmmm… didn’t realize that about Payne. Was thinking of having them quote for a Carrier anyway, seeing as the reviews I’ve found for Payne have been mixed.

        About the cost, I should have been more specific:
        this is a brand new system for the house (which has never had central before), so all new duct work, running new electrical and condensation lines.

        Given that, I feel comfortable with that price, but should I be concerned?

        • Well, for that price and for all new duct work I’d say it’s a fairly good deal. Ductwork alone usually costs $3-10K depending on the scope of the project. Just make sure you put a maintenance contract on it from a reputable company and have it tuned up 2x/yr!

          • thanks, Idaho! Do you recommend the same company (installers) do the maintenance? Or is it common to find some other third party to do the maintenance.

            We were actually thinking of foregoing the contract and just paying for a once-a-year tune up. Thoughts on that?

          • Using the contractor that installed it or not is a personal choice. Ideally if it is a good, reputable company you could use the same contractor. If it is new construction, I would advise against using the original installers. Also, It really does pay to have a yearly contract. 1 time a year is good for general cleaning. However, once the unit is a few years old having the 2x/ yr inspections will save you a ton on repairs (give you an idea of impending issues) as well as check out the individual seasonal components. Many folks that don’t have contracts find that the unit goes down when its 100+ degrees, not having a contract puts you at the back of the line with most companies. You would then have a 3-4 day + wait to get a repairman, whereas if you have a contract you will get same day or next day service plus discounted repairs. I hope that helps!

        • You were scaring the crap out of me. Wife really is hoping to get central heat/central AC next spring/fall. If the AC unit alone was going to be 10k for a knock-off Carrier, I am afraid that was going to push the time-table back a bit 🙂

          • Sorry, Kyle! Yeah, it’s actually a much bigger job than just the unit itself, when you add in all the brand new duct work, etc.

          • I got a brand new 2.5 tons Rheems in June for my roughly 1600 sq ft rowhouse, and it cost about $3,500. It was replacing another unit that was blown out by a power surge. Insurance paid.

  • I replaced my compressor and intake not four weeks ago. Depending on the unit chosen, the entire project cost varies significantly. When you begin price comparing as suggested above, ensure that the crane expense has it’s own line item. Once the boom truck arrived on the day of installation instead of the larger crane originally
    itemized, I went back to the AC contractor and negotiated down accordingly.

  • I work in Sales in this industry. ~7-8 K for a middle of the road higher efficiency 14/15 SEER-ish is what you should plan for. Too many variables to get much more detailed but 80% of all system replacements are in this range.

  • I have no idea about this kind of stuff but wonder if one shouldn’t also be worried about the added weight on the roof. Presumably if the roof can hold 20 inches of snow it should be able to hold a couple of A/C units, but I have no idea how much those things weigh and wonder if it should be a consideration.

  • I’ve had to replace both and the answer is it depends. For the compressor it depends on the size output. The larger one was much more expensive but I got the energy star rebate which price out to about the same as the smaller one that didn’t qualify for the rebate. I can remember the pricing exactly but the larger output was at least $4,000

    As for the Central Air I got mine for about $3,000 but it may be been a bit more.

    My house is a 2 BR with no negative access issues if that changes the price.

  • I’d also point out (echoing pablo.raw) that too big of a unit (no snickering, please) can actually be a bad thing and terribly inefficient, thereby costing you much more to run.

    Although it will make a whole lot of cold air, it can’t remove the humidity very well (I wish I could speak more intelligently about the reasons), leaving your home feeling like a cold, damp cave.

    Too small of a system and it will run all the time, struggling to cool the home. $$$

    • Not to mention…you can’t put a unit on the duct system that is a larger capacity than the duct can handle(air is invisibile but that doesnt mean you can crame anymore into a space than it is designed for)…Oversizing will, in essence, choke off the Air handler decreasing efficiency as well as the lifespan of the system drastically. On the other end, undersizing the system will decrease the CFM’s at every vent along the way and moreso the further you are from the air handling unit.

    • ah

      Basic reason is that to remove humidity the system actually needs to run a bit at the cold temperature–the water condenses on the coils and drips off. If you have too “big” a compressor then it won’t run long enough to pull the humidity out, it will just cool the air a lot without as much dehumidification.

  • Also consider the noise of the unit. My neighbor’s unit is too loud for me and the unit I installed for my basement apt. would bug the heck out of me if I slept there. (Though it hasn’t bothered any of the tenants.)

    And this goes more for condos, but could apply to row-houses as well – anytime you are thinking of major work – especially hiring a crane – check with your neighbors to see if anyone else might be ready to do similar improvements. At least share the cost of the crane, and maybe get a discount from the contractor for multiple jobs in one place.

  • had to replace my furnace this past winter and several HVAC contractors recommended I also replace my AC (including coil). The estimates came in between $7-8K including some revision of existing duct work.

    The quote to put the AC on the roof was an $500 for the crane.

    My house is 1200 square feet plus an additional finished basement. Hope this helps.

  • TaylorStreetMan: which contractor are you looking at that quoted about $10K? Planning to put in CAC in the next year or so.

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