SPLIT SYSTEM OR ROOFTOP?

HybridHeat Split systems instead of a "Rooftop" unit

Which costs more?


$10,000 HVAC Packaged Rooftop Unit.

– OR –

$20,000 Hybrid Heat “Split System.”


Do you know the answer?


Actually, it’s a trick question

 

 

The short answer is; “I don’t have enough information.”


The additional information necessary to determine which costs more should include average life expectancy, maintenance expense, and annual energy use.


Here is a sample analysis comparing a common rooftop to a Hybrid Heat split system (calculated by Carrier “OpCost” which utilizes a “Wrightsoft” heat load calculator backbone):


  • 120,000 BTU heating load, 5 ton cooling.
  • 14610 area code, $1.35 Therm gas cost, $.10 KWH electric cost.
  • Annual energy cost $3674/$5013.

The average split system lasts 15-25 years.  For this exercise I’ve assumed 17.  The average rooftop lasts 10-15 years.  For this exercise I’ve assumed 12. Also, I put the install cost of the split system high.   I find it’s better to under promise and over deliver, so these assumptions are skewed to the advantage of the rooftop.


Maintenance and repairs on rooftops is somewhat higher, but I have not factored that into my calculations. No assumption for increase in energy cost is factored in either.  Also not calculated, but assumed in the package costs is an energy recovery ventilation system on the Hybrid v/s fixed intake makeup air for the rooftop.  Makeup requirements could increase the disparity in energy use significantly depending on occupancy assumptions.


So, what is the “TOTAL ANNUAL COST” for both packages?  Depreciation of the Hybrid system (true annual purchase cost) is $1176 per year.  The rooftop is $833.  On its face the rooftop still looks cheaper, right? But when you add in energy cost, here is the annual result:


$4850 for the Hybrid split system, and $5846 for the rooftop.  The split saves $1000 per year! Put another way, total cost of the split including energy use is less then just the energy bill of the rooftop.


So why are rooftops the common “go to” answer? For a couple reasons:


First, in a large majority of cases there is a disconnect between initial cost and lifetime cost. Often the building owner and equipment decision maker is only exposed to initial cost, so incentive to reduce energy cost is not part of his equation. If the owner IS the tenant, they don’t associate higher equipment cost with lower energy cost (or vice versa).HybridHeat Split system instead of a "Rooftop"


The second disconnect is knowledge. How many HVAC Salespeople understand this opportunity, or want to risk bringing it up?


The third disconnect is time. For the HVAC Salesperson that does understand, the additional difficulty and time, not to mention reduced likelihood of making the sale, cause this approach to be a huge net looser.


Forth, and most important, is the consumer. If the consumer doesn’t start from a place of total cost they are unlikely to get this type of recommendation.


Better equipment costs more up front. This approach is not going to look advantageous if they are using an initial cost or “low bid” replacement strategy.

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  • Therefore operating costs are often lower than those of central systems that cool every room whether it is in use or not..If you cannot afford to purchase an air conditioner for the whole house you can also buy the system one zone at a time. Split-system air- conditioners cost about 1 500- 2 000 per ton 12 000 Btu h of cooling capacity. This is about 30 more than central systems and may cost twice as much as window units of similar capacity..The installer must judge the best location for the air handling unit.

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