4.5 kW class
4.5 kW split systems, compared on the figures that matter.
A 4.5 kW unit typically suits a living room in a smaller home — roughly 21 to 41 square metres depending on which way it faces, how well it is insulated and how many people use it. 21 models in this class are registered for sale in Australia across 4 brands.
Quick answer
A 4.5 kW split system air conditioner suits a room of roughly 21 to 41 square metres — typically a living room in a smaller home — with the exact figure depending on orientation, insulation, ceiling height and occupancy. 21 distinct 4.5 kW-class models are registered with the Australian Government's GEMS database across 4 brands: Daikin, Fujitsu, Mitsubishi Electric, Mitsubishi Heavy Industries. In this class the best cooling efficiency figure is AEER 4.17 and the best heating efficiency figure is ACOP 4.59, and the lowest declared indoor noise level is 54.6 dB. Thunderman Electrical and Air Conditioning Services supplies and installs units in this class across Greater Melbourne under ARCtick certification, with electrical work by REC 28523.
What this size means on the job
The part a showroom won't tell you.
4.5 kW is the thinnest class on the register, and that itself is useful information: only four of the eight brands bother to register a unit in this band, because most manufacturers jump straight from 3.5 to 5 kW. If a room genuinely sits between those two sizes, the practical answer is usually to work out which way the sizing calculation errs and take the neighbouring class rather than hunt for a 4.5. The exception is a room where the 5 kW would be oversized enough to short-cycle, which costs efficiency and comfort and shortens the compressor's life.
Quietest in this class
Ranked by declared indoor noise.
In this class the declared indoor noise levels run from 54.6 dB to 62 dB — a spread of 7 dB between the quietest and the loudest, which is a difference you would hear plainly in the same room.Capped at three models per brand so one range cannot fill the table.
| Model | Cooling | Heating | Indoor noise | AEER | ACOP | Stars | Registration |
|---|---|---|---|---|---|---|---|
| Mitsubishi ElectricMSZ-EF42VGDB+6 variants | 4.2 kW | 5.4 kW | 54.6 dB | 3.49 | 3.7 | 3 / 2.5 | AAC8152 |
| Mitsubishi ElectricMSZ-AP42VGD+3 variants | 4.2 kW | 5.4 kW | 56.4 dB | 3.52 | 3.77 | 3.5 / 2.5 | AAC6358 |
| FujitsuASTH14KNCA | 4.2 kW | 4.7 kW | 57 dB | 3.41 | 4.15 | 3.5 / 3 | AAC6443 |
| Mitsubishi Heavy IndustriesSRK45ZSPA-W | 4.5 kW | 5 kW | 57 dB | 3.22 | 3.63 | 2.5 / 2.5 | AAC9920 |
| FujitsuASTH14KMCD | 4.2 kW | 5.4 kW | 58 dB | 3.64 | 3.85 | 4 / 2.5 | AAC7488 |
| Mitsubishi ElectricMSZ-AP42VGD+3 variants | 4.2 kW | 5.4 kW | 58 dB | 3.52 | 3.77 | 4 / 2.5 | AAC7722 |
| DaikinFTXM46AVMA | 4.6 kW | 4.7 kW | 59 dB | 4.17 | 4.59 | 4 / 3.5 | AAC10032 |
| DaikinFTXM46W2VMA | 4.6 kW | 4.7 kW | 59 dB | 3.93 | 4.49 | 4 / 3.5 | AAC6755 |
Cooling and heating are rated capacity. AEER andACOP are the annual efficiency figures for cooling and heating — higher is cheaper to run. Stars are shown as cooling / heating for a mixed climate zone, which is the one Melbourne sits in. Indoor noise is the manufacturer's declared sound level for the indoor unit. Every figure is as registered with the Australian Government's GEMS register, and the registration number is there so you can look it up yourself.
Cheapest to run — cooling
Ranked by AEER.
Cooling efficiency in this class runs from AEER 3.22 to 4.17 — the best unit here delivers about 30% more cooling per unit of power than the weakest. That gap is what you are choosing between, and it does not show up on the star sticker, because stars are banded.
| Model | Cooling | Heating | Indoor noise | AEER | ACOP | Stars | Registration |
|---|---|---|---|---|---|---|---|
| DaikinFTXM46AVMA | 4.6 kW | 4.7 kW | 59 dB | 4.17 | 4.59 | 4 / 3.5 | AAC10032 |
| Mitsubishi Heavy IndustriesSRK42ZTA-WF+2 variants | 4.2 kW | 5.4 kW | 59 dB | 4.05 | 4.04 | 4 / 3 | AAC10042 |
| DaikinFTXV46AVMA | 4.6 kW | 4.7 kW | 60 dB | 4.02 | 4.07 | 3.5 / 2.5 | AAC10274 |
| DaikinFTXM46WVMA | 4.6 kW | 4.7 kW | 59 dB | 3.94 | 4.5 | 4 / 3.5 | AAC10190 |
| FujitsuASTH14KMCD | 4.2 kW | 5.4 kW | 58 dB | 3.64 | 3.85 | 4 / 2.5 | AAC7488 |
| Mitsubishi ElectricMSZ-AP42VGD+3 variants | 4.2 kW | 5.4 kW | 56.4 dB | 3.52 | 3.77 | 3.5 / 2.5 | AAC6358 |
| Mitsubishi ElectricMSZ-AP42VGD+3 variants | 4.2 kW | 5.4 kW | 58 dB | 3.52 | 3.77 | 4 / 2.5 | AAC7722 |
| Mitsubishi ElectricMSZ-EF42VGDB+6 variants | 4.2 kW | 5.4 kW | 54.6 dB | 3.49 | 3.7 | 3 / 2.5 | AAC8152 |
Best for a Melbourne winter
Ranked by ACOP — the heating figure.
Heating efficiency here runs from ACOP 3.63 to 4.59, a spread of about 26%. Because Melbourne runs a reverse-cycle system for warmth far more of the year than for cooling, that spread costs more over time than the cooling one does — and this ranking is rarely the same as the one above it.
| Model | Cooling | Heating | Indoor noise | AEER | ACOP | Stars | Registration |
|---|---|---|---|---|---|---|---|
| DaikinFTXM46AVMA | 4.6 kW | 4.7 kW | 59 dB | 4.17 | 4.59 | 4 / 3.5 | AAC10032 |
| DaikinFTXM46WVMA | 4.6 kW | 4.7 kW | 59 dB | 3.94 | 4.5 | 4 / 3.5 | AAC10190 |
| DaikinFTXM46W2VMA | 4.6 kW | 4.7 kW | 59 dB | 3.93 | 4.49 | 4 / 3.5 | AAC6755 |
| FujitsuASTH14KNCA | 4.2 kW | 4.7 kW | 57 dB | 3.41 | 4.15 | 3.5 / 3 | AAC6443 |
| Mitsubishi Heavy IndustriesSRK42ZTA-WF+2 variants | 4.2 kW | 5.4 kW | 59 dB | 4.05 | 4.04 | 4 / 3 | AAC10042 |
| FujitsuASTH14KMCD | 4.2 kW | 5.4 kW | 58 dB | 3.64 | 3.85 | 4 / 2.5 | AAC7488 |
| Mitsubishi ElectricMSZ-AP42VGD+3 variants | 4.2 kW | 5.4 kW | 56.4 dB | 3.52 | 3.77 | 3.5 / 2.5 | AAC6358 |
| Mitsubishi ElectricMSZ-AP42VGD+3 variants | 4.2 kW | 5.4 kW | 58 dB | 3.52 | 3.77 | 4 / 2.5 | AAC7722 |
Not sure this is the right size?
Look either side.
All figures from the GEMS registration database (Australian Government). Every model above carries its registration number so you can check it atthe register.
4.5 kW air conditioners — common questions
Should I get a 4.5 kW unit or go up to 5 kW?
Most of the time, 5 kW — simply because the choice is far wider and the price difference at that capacity is rarely the deciding factor. The register carries only a small number of 4.5 kW models across a handful of brands. The case for staying at 4.5 kW is a room that is genuinely borderline, where a 5 kW unit would cycle on and off rather than run steadily.
How many 4.5 kW models are sold in Australia?
21 distinct models in this capacity class are currently registered with the Australian Government's GEMS database, across 4 brands: Daikin, Fujitsu, Mitsubishi Electric, Mitsubishi Heavy Industries. That count is registrations rather than shelf listings — a single registration often covers several colourways of the same unit, which is why a retailer's catalogue looks larger.
What is the quietest 4.5 kW air conditioner?
The lowest declared indoor sound level in this class is 54.6 dB. Noise figures are declared by the manufacturer at a stated fan speed, so they compare like with like between models but will not match what you measure in a room — where the mounting position, the wall and the furnishings all change what you hear. A unit that is quiet on paper and badly positioned will still be the loudest thing in a bedroom.
Does a 4.5 kW unit heat as well as it cools?
Not necessarily, and in Melbourne that is the question worth asking. In this class the best cooling efficiency figure (AEER) is 4.17 and the best heating figure (ACOP) is 4.59, and they usually belong to different models. Because a reverse-cycle system here runs for warmth far more of the year than for cooling, the heating figure generally deserves more weight than the cooling star rating a showroom will point at.
Right size, wrong switchboard is still the wrong job.
Yiannis will confirm the capacity against the actual room, check the board can carry it, and quote the whole job rather than the easy half. Free quote, ARCtick certified, REC 28523.