What Size Ducted Air Conditioner Do I Need?
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Bigger isn't better: how we size ducted systems
The size of a ducted system is measured in kilowatts (kW), and it’s one of the most important decisions in the whole job. Too small and the house never gets comfortable on the hottest and coldest days. Too big and you pay more upfront, the system runs less efficiently, and you may not get the comfort you expected. Here’s how we work it out.
Start with the floor area, then adjust
As a starting point we work on roughly 130 to 140 watts per square metre of conditioned floor area. That gives a raw figure, which we then adjust for the things that really change the load: ceiling height, insulation, the amount of glass, which way the living areas face, and how exposed the site is.
Why zoning means a smaller unit
With a zoned system you rarely heat or cool every room at once. You run the living zone during the day and the bedrooms at night. Modern inverter units can also ramp up above their rated capacity for short periods. Together, that means the right unit is often smaller than the raw floor-area figure suggests. For example, a typical four-bedroom home of around 180 square metres might work out at well over 20 kW on paper, but with four zones an 18 kW system is often the right fit.
The problem with oversizing
Some quotes push the biggest system available. It costs more, can short-cycle (switching on and off too often), and doesn’t make the house more comfortable. The Victorian Government has also flagged oversizing as a concern in the VEU program. We size to the house, not the price tag.
Ductwork matters as much as the unit
A well-sized unit on a poorly designed duct layout still won’t perform. We place the indoor unit centrally so duct runs stay short and even, split the main ducts into balanced branches, and size each outlet to the room it serves.
Get it sized properly
Every quote we do starts with a site visit, where Bailey measures up and designs the system for your home. If you’re replacing gas ducted heating, you may also be eligible for the VEU rebate. You might also like our guide to running costs.
TRUSTED WORK. PROVEN RESULTS Across the Peninsula.
A look inside the homes and businesses we’ve serviced across the Mornington Peninsula. Real projects, real results, real satisfaction.
See the results delivered by a crew chosen for their expertise, professionalism,
and dedication to doing things right.
How we size your system
Measured on site
Floor area, ceilings, glass and exposure all checked.
Zoning factored in
A smaller, more efficient unit where zoning allows.
Balanced duct design
Short, even runs from a central unit.
No oversizing
Sized to the house, not the price tag.
WHAT OUR CUSTOMERS SAY
From urgent repairs to full installations, we deliver safe, efficient, and long-lasting heating and cooling solutions backed by years of trusted expertise.
A big thank you to Bailey and his team for excellent service for our recent central heating unit installation. Arrival time was spot on and all worked hard to achieve a quality install. Price was excellent and product exactly what I asked for. No mess was left and everything went as planned.
Just had the pleasure of meeting Bailey and Team when they came to replace our old broken down ducted heater. The job was done efficiently, smoothly and quickly and what a friendly team they are too. Highly recommended.
Had issues with our gas ducted heating and contacted Bailey who came out quickly. He diagnosed the issue after checking the system; a part needed to be ordered. As soon as this was received, Bailey was quick again to come out and fix it. In Melbourne’s current cold weather, it was a godsend! Will call him back for any future issues &/or servicing.
Bailey and his team came to install my units today, they where all very professional and very easy to work with, they knew exactly where I wanted the units to go and they where really fast and prompt. Highly recommend Mornington heating and cooling, very happy with the results thanks so much guys!
Bailey
Owner of Mornington Heating and Cooling
For over 15 years, Mornington Heating & Cooling has been the go-to for Ducted Reverse Cycle Air Conditioning Installation across the Mornington Peninsula, including the Mornington Peninsula.
With a dedicated team of fully certified technicians, every project is approached with a commitment to quality and customer satisfaction.
The focus is on delivering reliable climate control solutions that adapt to the unique needs of each home or business.
Passionate about providing comfort across all seasons, the team prioritises long-term performance and dependable results. Trust in us for your heating and cooling needs, ensuring your space remains comfortable year after year.
For over 15 years, Mornington Heating & Cooling has been the go-to for Ducted Reverse Cycle Air Conditioning Installation across the Mornington Peninsula, including the Mornington Peninsula.
With a dedicated team of fully certified technicians, every project is approached with a commitment to quality and customer satisfaction.
The focus is on delivering reliable climate control solutions that adapt to the unique needs of each home or business.
Passionate about providing comfort across all seasons, the team prioritises long-term performance and dependable results. Trust in us for your heating and cooling needs, ensuring your space remains comfortable year after year.
Why the Mornington Peninsula Homeowners Choose Mornington Heating & Cooling
More than just heating and cooling – our team shows up committed to delivering a result you can rely on, with quality work and attention to detail from start to finish.
Over 15 Years of Service
With more than 15 years in the industry, Mornington Heating & Cooling has built a reputation for reliable heating and cooling installation across the Mornington Peninsula. Experience means peace of mind for every customer.
Fully Certified Technicians
All technicians at Mornington Heating & Cooling are fully certified professionals, ensuring that every heating and cooling installation is handled by qualified experts who prioritise quality and safety.
Local Business Commitment
As a local business serving the Mornington Peninsula, Mornington Heating & Cooling is dedicated to the community, providing personalised service and climate control solutions designed to meet local needs and conditions.
Trusted Installation Methods
Utilising proven installation methods, Mornington Heating & Cooling ensures that every ducted reverse cycle air conditioning installation is performed with care, ensuring long-term performance and reliability for every system.
Every team member is selected not only for their skill and experience but also for their professionalism, politeness, and respectful nature.
About Mornington Heating & Cooling
Experience ultimate comfort with Mornington Heating & Cooling, your go-to for Ducted Reverse Cycle Air Conditioning Installation.
For more than 15 years, Mornington Heating & Cooling has been delivering reliable air conditioning installation, ducted heating repairs, and comprehensive climate control solutions throughout the Mornington Peninsula.
Our certified technicians are dedicated to providing services like Air Conditioning Installation, Ducted Split System Installation, and Gas Ducted Heating Installation.
We proudly serve areas like Mount Martha, Rye, and Blairgowrie. If you’re searching for Heating & Cooling Installation near me, reach out today for a quote and let us enhance your indoor comfort!
Our step by step approach
We keep things simple – from consultation to completion, here’s how we deliver concrete work you can rely on.
Quick Home Assessment
We visit your home to understand the space and what you need from your heating or cooling system so we can recommend the right solution.
Clear Recommendation & Quote
We explain the best system for your home and provide a straightforward quote so you know exactly what to expect.
Show You How It Works
Before we leave, we walk you through how to use your new system and answer any questions so you feel confident using it.
System Testing & Setup
We test the system, check airflow and performance, and make sure everything is running smoothly.
Professional Installation
Our team installs your new heating or cooling system carefully, making sure everything is fitted properly and ready to run.
See the results delivered by a crew chosen for their expertise, professionalism,
and dedication to doing things right.
Sizing questions
How many kW do I need for my house?
It depends on floor area, ceiling height, insulation, glass and exposure. As a starting point we use roughly 130 to 140 watts per square metre, then adjust and factor in zoning.
Is a bigger system better?
No. An oversized system costs more and can run less efficiently. The right size keeps the house comfortable without wasting energy.
Why does zoning reduce the size?
Because you rarely run every room at once. You heat or cool the zones in use, so the unit does not need to cover the whole house at full load.
Can I reuse my old gas ductwork?
Usually not. Old gas ductwork often was not designed for cooling, so we normally install new insulated duct sized for the new system.
How do I get a proper sizing?
Book a free site visit. Bailey measures up and designs the system before quoting.
