Is 16Kw Enough for a Heater/Aircon in a Large 4 Bedroom Home?

I'm looking at replacing my heater/air condition in my house.
It is 4 bedroom, 2 living. The original house plans show is being a 25.7 square house (or 238.7 sqm).
Taking the bathrooms, laundry, walk-in robe etc out, it is roughly 170 sqm.
We have 2.7m high ceilings.

I've had a few quotes.
1 insists a 22kW system is needed.
The other one I looked at is saying that the Daikin FDYA160 16kW system will be adequate as it will be setup with MyAir and that if we don't run all zones at the same time, he is confident it is sufficient. Also said this system can do 17kW on cooling and 20 on heating.

A few online calculators give me different results. The Actron calculator is telling me 27kW, another one said 22kW and another said 18kW.

Does 16kW sound like enough for a largish 4 bedroom home?
We have 3-phase available, so is there any harm in going a slightly bigger system, such as a 18 or 20?

Last thing we want is to spend 15k on a new system and it not really be adequate enough.


  • -1

    go for the 22kW

  • 16kw will do it just more slowly. but yeah go bigger no regrets

  • Similar size to my house, we installed a 27kw system.

  • +1

    16kw will be sufficient. We have similar sized place as yours with 2.7m ceilings. 4 BR, 2 bath, walk in and 2 lounge areas. We did 3-4 zones so only heating/cooling areas that we are using as we don't expect to do the entire house. Though ours is only single phase power anyways.

    Since you have access to 3 phase, go the slightly larger system is my suggestion if the price is ok then go for it.

  • Also consider where you have temperature sensors. We paid extra to get aircon that could do an individual zone. Only really want to do that a few times/yr but because there’s only one main sensor, if you have on zones without a sensor it gets freezing fast. Too many other things to think about when building and didn’t get good advice on that topic.

  • Consider the energy star rating as well, a bit higher cost may save you heaps in long term.

  • +3

    Get as big as you can afford. Remember the saying, "640k of RAM is enough for anyone".

    • +2

      Yes, global warming ;)

      • +2

        You kids ;)

  • +1

    16kw might be ok if your home is well insulated and doesn't have a high heat load from east/west facing windows.

  • +1

    Always go for the bigger system. It will get your home cooler/warmer quicker that not only is simply a better experience, but will also cater for those occasional extreme days without (hopefully) running at capacity for hours on end.

    On the side, why are you removing the bathrooms, laundry, walk-in robe, etc. from your calculation? Yes, I can understand these areas might be relatively easily closed off in theory, but in practice they are often left open, or when you do go in them you have a volume of air that is significantly warmer or cooler than the rest of house. This body of air can quickly escape and you end up heating/cooling it in any event.

  • The aircon you've mentioned you're replacing - how many kW is that one and can you use that as a relative measure?

    • +1

      Not sure, it was here when we got here a d it doesn't work properly so it's hard to compare.

  • I have 14kW for a 3br 2 living area house with no wall insulation. It really comes down to how much of the house you want to cool at once. If you will be regularly cooling the entire house, the 22kW would be better. If you use the zoning to only cool half the house, the 16kW would be fine. The tradeoff with going a larger system is there will be a minimum number of zones that need to be open. For example with my 14kW the minimum I can run is two zones. With the 22kW you would likely need a minimum of 3 zones open.

  • I have 14kw and it's fine for a 4 bed 2 bath 2 living room home. Ceilings not as high though. Good roof insulation and double glazed windows and verandahs. Sadly no wall insulation - except in the new extension area.

  • 16kW will be just fine. I don’t feel it to be slow in doing it’s job in a larger house than what you specified.

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