Split system installation Melbourne: the 2026 buyer's guide

Split system aircon is Melbourne's default cooling and heating for anything smaller than a full ducted retrofit. If you get the sizing right and the install done properly, one 5 kW unit runs the main living zone of an average Berwick-sized brick veneer for a decade with almost zero maintenance. Get it wrong and you're either replacing the unit at year 5 or running it flat-out on the hottest day and it still can't keep up.

How to actually size a split for a Melbourne room

The rule of thumb everyone quotes is 100W of cooling per square metre, a 4m × 5m bedroom is 20 m² × 100 = 2 kW so buy a 2.5 kW unit. That's a starting point but Melbourne throws in some wrinkles:

• West-facing glass at afternoon sun: add 30% to the load
• Cathedral ceiling or double-height: add 20-40%
• Poor insulation (older Berwick/Officer weatherboards): add 25%
• Ceiling fan already in the room: subtract 10%

So a 4×5 west-facing bedroom in an older weatherboard: 20 × 100 × 1.3 × 1.25 = 3.25 kW → we'd spec a 3.5 kW unit, not a 2.5. Undersizing is the single biggest reason customers ring us to replace a unit at year 3.

Common Melbourne room sizings

• Small bedroom, well-insulated: 2.5 kW (e.g. Mitsubishi MSZ-AP25)
• Master bedroom or study: 3.5 kW (MSZ-AP35)
• Open-plan living / dining, average glass: 5.0 kW (MSZ-AP50)
• Large living or great-room: 6.0 kW or 7.1 kW (MSZ-AP60/71)
• Cathedral-ceiling great-room: 8.0 kW+ or move to multi-head

Brand pick, Mitsubishi vs Kaden vs everything else

We install two split-system brands as our defaults: Mitsubishi Electric and Kaden. Two, not twelve, because we'd rather know two ranges properly than carry a catalogue we can't stand behind. We dropped several others over the last few years because the failure rates weren't worth the warranty admin. Full range and our take is on the /brands section, the short version:

• Mitsubishi Electric MSZ-AP: our default. Quieter on low fan, under 1% failure rate across the range, and the parts pipeline is still open on units we put in a decade ago.
• Mitsubishi Electric MSZ-FH (Hyper Heating): the one for the Dandenong Ranges. It holds rated heating output down to -15 °C where a standard split has already given up about 30% of it.
• Kaden KSI-v3: the one when a family wants three bedrooms done in one visit rather than one a year. Reece-exclusive, so parts are in every store in Victoria, 5-year warranty.
• Everything else: we'll install what you specify, but these are the two ranges we know inside out.

What a proper install day looks like

A standard split system install is a half-day for one unit. Here's what should happen, and what the $99-a-day mobs skip:

• Vacuum-purge the refrigerant lines to at least -500 microHg (removes moisture that would eventually degrade the compressor)
• Nitrogen pressure test the lines to confirm no leaks BEFORE releasing the factory refrigerant charge
• Mount the outdoor unit on wall brackets or a purpose-made stand, never straight on the ground
• Wrap and duct-tape the line-set weather cover neatly (visible from the yard, not the neighbour's problem)
• Test the unit in cool AND heat for 20 minutes minimum, confirm temperatures at the vent, sign the compliance certificate

If the installer doesn't have a vacuum pump on the truck, they're not vacuum-purging. If they don't have a nitrogen bottle, they're not pressure testing. These are the two easy-to-check signals of a proper job.

What Melbourne installs actually cost

Fully installed prices we quote regularly, includes the unit, standard 3m back-to-back install, wall bracket, and compliance certificate:

• 2.5 kW MSZ-AP25 installed: $2,190
• 3.5 kW MSZ-AP35 installed: $2,390
• 5.0 kW MSZ-AP50 installed: $2,690
• 7.1 kW MSZ-AP71 installed: $3,290
• Kaden Bold equivalents: $500-700 less than Mitsubishi at each size

Add ~$300 for extended pipe runs (>5m), ~$500 for a first-floor install with roof access, ~$200 for salt-tolerant coil coating (Tooradin, Lang Lang coastal edge).

What to ask the installer

Three questions that tell you everything:

• Do you vacuum-purge and nitrogen-pressure-test? (Should be yes, no hesitation)
• What's the workmanship warranty on top of the manufacturer warranty? (We do 6 years, bare minimum should be 5)
• Will the person who quoted me be on the tools? (Small-business red flag if the answer is 'no, we send a sub-contractor')