A split system is the default way Melbourne heats and cools now, and for good reason — a modern inverter unit is the cheapest way to heat a room in this city, gas included.
These are the five questions we get asked most when we’re quoting one.
1. What size do I need?
The most important question, and the one most often answered badly — usually by someone guessing from the room’s floor area alone.
As a rough starting point, allow around 125–160 watts of capacity per square metre. So a 4m × 5m living room is 20m², which puts you somewhere around 2.5–3.2 kW.
But floor area is only the beginning. What actually moves the number:
Ceiling height. A 3.3m ceiling in a period home is a third more air than a 2.4m one.
Glazing. Large west-facing windows are the single biggest load in a Melbourne house. A room with a wall of west-facing glass can need substantially more capacity than its floor area suggests.
Insulation. An insulated 1990s house and an uninsulated 1920s weatherboard behave completely differently.
Orientation and shading. North and west rooms run hot; south rooms stay cool.
Open plan. If the room opens onto a hallway or another living area, you’re conditioning more than one room whether you intended to or not.
Getting it wrong in either direction is a problem. Undersized, the unit runs flat out, never quite gets there, and wears out early. Oversized, it short-cycles — cooling the air quickly, switching off before it’s removed any humidity, then starting again. Short-cycling is hard on the compressor and leaves the room feeling clammy rather than comfortable.
We’d rather spend ten minutes measuring than have you buy the wrong unit.
2. Where should the indoor and outdoor units go?
Siting affects performance more than most people realise.
The indoor head wants to be high on a wall with a clear throw across the room — not tucked into a corner or blocked by a wardrobe or a pelmet. Don’t put it directly above where you sit; nobody enjoys being blown on continuously. And it needs a drain path with fall to somewhere sensible.
The outdoor unit wants shade, airflow and distance from bedroom windows. A west-facing wall in full afternoon sun makes the unit work considerably harder on exactly the days you need it most. Keep at least 300mm clear around it, don’t box it in behind decking or screening, and think about your neighbours — condenser noise at 11pm is a common source of grievance.
Pipe run length matters. The shorter and straighter the run between the two units, the better the system performs. Long runs lose capacity. If the ideal indoor position is 15 metres from the only viable outdoor position, that’s worth knowing before you commit.
3. Can my switchboard handle it?
This is the question nobody asks and everybody should.
A split system needs its own dedicated circuit and an isolator. In a modern home with a modern board, fine. In the period homes through Hawthorn, Kew and Camberwell, we frequently open the board and find no spare ways, no RCD protection, and consumer mains that were sized for a very different house.
That doesn’t mean you can’t have air conditioning. It means the switchboard upgrade is part of the job, and you should know that when you’re budgeting rather than on installation day.
If you’re putting in multiple systems, or ducted, or you’ve also got an EV charger in mind, that’s the point at which three-phase power becomes worth costing.
4. What does it cost to run?
Less than people think, if it’s a modern inverter unit and you use it sensibly.
Reverse-cycle air conditioning is the most efficient electric heating available — for every unit of electricity it draws, it moves several units of heat. That’s why it’s cheaper to heat a room with a split system than with a gas heater or a resistive electric heater, despite electricity costing more per unit than gas.
Three things that make the biggest difference to your bill:
Thermostat setting. 24 in summer, 20 in winter. Every degree beyond that costs roughly 5–10% more.
Zone rather than whole-house. Heat the room you’re in. This is where split systems beat ducted for most households.
Run a ceiling fan with it. It lets you set the thermostat two to three degrees further from ambient for the same comfort.
If you’ve got solar, run it during the day and let the house coast into the evening. It’s the cheapest cooling you’ll ever get.
5. Who installs it — an electrician or a refrigeration technician?
Both, and this is worth understanding because it affects who you call when something goes wrong.
The refrigeration work — mounting, pipe work, evacuating and charging the system — requires a refrigerant handling licence.
The electrical work — the dedicated circuit, isolator, switchboard work and connection — requires a licensed electrician.
Plenty of installations are done by a team covering both. What you want to avoid is the arrangement where the electrical side is treated as an afterthought, because that’s where you get undersized circuits, missing isolators and no Certificate of Electrical Safety.
Ask who’s doing the electrical work and whether you’ll get a certificate. If the answer is vague, that tells you something.
What we do
We handle split system installation and all the electrical work around it — sizing, siting, the dedicated circuit, any switchboard work, and the certificate at the end.
We’ll tell you what size you need rather than what’s on special, and we’ll tell you if your board needs attention before we start rather than after.
Registered Master Electrician. Over 200 five-star Google reviews. Lifetime workmanship warranty.
Related: Air conditioning failure and repair · Air Conditioning Installation Near Me
