My understanding is that a variable speed compressor permits greater efficiency and reduce wear & tear. Assume application is in Florida, not NYC.

  • Is there a range for the cost premium for such systems?
  • What is the typical efficiency saving associated with systems?
  • Do variable speed compressors have higher failure rates than their fixed counterparts?
  • Is there any other factors that should be considered when choosing whether or not to select inverter technology?

Any lessons learned are always appreciated.

3 Answers 3


The simplest question can have the most complex answer at times. I'll try to help. Variable speed systems have some advantages over single stage or single speed systems. For Florida I would say the best benefit is that it allows the system to be optimized for dehumidification in cooling. The fan slows down and the cooling coil gets colder and pulls more moisture from the air. This adds to comfort as well as reducing the risk of mold growth in the conditioned part of the home. If any heat pump system is properly sized for cooling it will almost certainly provide all the heat you need without strip heat to supplement. There is another choice which is 2-stage or 2-speed. In this case the high speed is reserved for the dog days and the unit will run on low on cooler days and in the evening. This may be a good choice. Reputable manufacturers will warranty their compressors for 10 years and I recommend Carrier, Trane and York as top brands. Be sure you save your purchase documents and register the installation. The most important thing I can add is that it's true that you get what you pay for. If you look for the lowest cost you get not only the lowest cost equipment but also a contractor perhaps less trained, less equipped and willing to cut corners that will affect you for years. It is my belief that when you see bad reviews it is more likely the contractor earning the score and not the equipment. So I recommend you pick your contractor first and allow them to customize the system to your needs.

  • You are dead-on when you say that it's the contractor that can tank the review scores of a piece of equipment. Even the finest piece of HVAC hardware on the planet can be ruined by dodgy ducts or bad sizing -- ACCA didn't write Manuals J, S, and D to sit on a shelf, gathering dust! Jan 27, 2019 at 20:05
  • We can all talk about hypotheticals all we like. Do whatever the guy who does the math says to do, +1.
    – Mazura
    Jan 28, 2019 at 3:34
  • @Mazura -- as long as they aren't keen on ruining all the math with a ductopus in your attic, that is! Jan 29, 2019 at 1:05

I've never done a heat pump so I've no idea, because

Homeowners who live in extreme climates have been traditionally left out in the cold when it comes to the ductless cooling and heating revolution.

Assuming the new (meaning expensive?) technology works, that means you can now use a heat pump in climates where you couldn't before... I guess.

Their selling points (none of which can't be achieved by a well balanced normal split system) : "Consistent Room Temperature - No Ups and Downs, Ons and Offs" - "Consume Only The Energy You Need" - "Heats Up Quickly" ... all of those are intrinsic to a well-installed system of any kind.

"Energy Use is Even and Steady" - that's the only difference. How 'real' it is, idk.

From what I understand, if you can get away with a heat pump that's awesome. You living in NY and me in Chicago, can't. But even if it works, is it a $20k dollar unit? You get one of three things: comfort, efficiency, or environmentalism. Tweaking it to add more than one just costs extra money. Bottom line IMO is ROI levied against comfort.

  • Where do you put the fresh air intake... What happens to the V in HVAC if you don't have any ducts?
    – Mazura
    Jan 27, 2019 at 18:04
  • The ventilation system would be separate from the interior air-handling in this case -- it's similar to what you'd do if you had direct fan coil/radiator or radiant floor hydronics. Jan 27, 2019 at 18:11
  • Also, heat pumps are still useful in places like NY and Chicago since you spend way more time above the economic balance point than below, even in cold climates. (At the very least, they mean you aren't burning fuel during the spring and fall "shoulder seasons"...) Jan 27, 2019 at 18:13
  • One other thing -- inverter heat pumps are available in the traditional North American split system form factor, btw, not just in the "mini-split" form factor that's more common in other places in the world Jan 27, 2019 at 18:17
  • 1
    Yeah -- "just a heat pump" isn't really a thing for heat anyway due to defrost cycles. In a climate like yours or mine, I personally would be inclined to rock a heat pump system with hydronic backup heat (instead of a more conventional forced-air furnace or electric strips for the backup/emergency heat) -- with this you have neither the service-capacity issues of electric strips, nor the "hard cutover" issues of a forced-air furnace in a dual fuel system Jan 27, 2019 at 18:22

Inverter technology has come a long way. It is cheaper to run the system. As with most things add more bells and whistles and they are prone to earlier failure. The last system I installed had a 10 year warranty that is super in my opinion. As far as the question about make up air it depends on the system. Mini split systems do need a separate vent and a very small fan can bring outside air in the home when the system is running or on a timer. For central air heat pumps a vent is added for outside air on the intake side of the air handler so when the system is running fresh air is pulled in and conditioned. To recap, an inverter based heat pump will save $ to run and many are becoming much more efficient and some work into the low teens without auxlary or emergency heat strips. A good quality is important for long life, if you find one at 1/2 the price of a top name brand don't expect it to last as long or even 1/2 as long from what I have seen.

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