Why two quotes for the same house differ

A ducted system is designed for your house, so two installers can quote the same home and land a long way apart. The gap is usually a mix of how the capacity was worked out, how many outlets and zones are proposed, the controls, how hard your roof space is to work in, where the outdoor unit goes, whether an old system has to come out, and what is included.Compare the parts rather than the totals. The ACDA Standard requires every accredited member's quote to set out the calculated capacity, the system in full, the price and payment schedule, inclusions and exclusions, the warranty period and the recommended servicing frequency. Each cost below sits under one of those headings.

Capacity comes first

The biggest single driver of price is the heating and cooling capacity your home needs. The Standard requires an accredited member to work this out with an approved calculation method, not a rule of thumb.Capacity sets the size of the outdoor unit, the indoor unit and the ducting, so a quote built on a proper calculation can come in higher than one built on a guess. Too small and the system runs flat out on the hottest days and still falls short. Too big and you pay for capacity you never use. The ACDA e-guide makes the same point: more is not necessarily better.On the quote, look for the calculated capacity for heating and cooling. If it is missing, ask for it. If two quotes differ widely, ask each installer how they arrived at their figure.

Outlets, zones and controls

Every outlet adds a duct run, a ceiling fitting and labour, so a quote that conditions every room costs more than one that covers the living areas and two bedrooms. Neither is wrong, as long as the quote shows how many outlets and where each goes.Zoning lets you shut off the parts of the house you are not using, and the ACDA e-guide gives the everyday example: living rooms by day, bedrooms at night. It adds a controller and the hardware to close each zone, so it raises the installed price, but it is the main reason a well designed ducted system costs less to run. Smart zoning, with a sensor and control in each zone, costs more again.The Standard requires the quote to describe the system: manufacturer, actual capacity, the number and location of outlets, the zones and the controls.

Roof space, duct runs and the outdoor unit

The same equipment costs more to install in some houses than others. A tight or low roof space, a steep roof or an upstairs ceiling with no easy access all add hours, and long duct runs to far rooms use more ducting and labour.The outdoor unit needs shade, airflow and room to get rid of the heat it pulls from the house. The further it sits from the indoor unit, the longer the pipe and cable run. It may need a plinth and a power supply, which can mean electrical work. Removing and disposing of an old system is a cost of its own.The Standard lists what an accredited member's quote must mark as included or excluded: power supply, supports or plinth, drainage, covers for exposed piping and wiring, and clean-up and rubbish removal. Add exclusions back before you compare totals.

Why the cheapest quote can cost more to run

A low total usually means something has been left out, and the missing item often turns up on your power bill rather than your invoice. A guessed capacity can leave you with a system that struggles on the days you need it most. A single zone means you condition the whole house to cool one room. Exclusions come back as extras.A properly sized, zoned system reaches the set temperature without running flat out and only conditions the rooms in use. The ACDA e-guide puts it simply: the smaller the area you moderate, the lower the energy consumption. It also recommends a professional service at the start of each cooling season, which is why the Standard requires the quote to state the warranty period and recommended servicing frequency.If the first proposal is beyond your budget, say so. The Standard requires a member to suggest alternatives where appropriate and, if you ask, give indicative pricing for each.

If the installation falls short

Part of what you pay for is what happens if the work is not right. Every new domestic installation by an accredited member is covered by the ACDA Guarantee: a written workmanship guarantee on contracts up to $25,000 including GST, resolved by independent Chartered Engineer review. It is not an equipment warranty or a price guarantee, and it applies in addition to your rights under Australian Consumer Law.If you have a concern, complete the Dispute Resolution Form with your details, the member's details, what was installed and when, and what the problem is. Attach your quote, your invoice and any photographs, and send it to the Dispute Resolution Committee, PO Box 253, Emu Plains NSW 2750, or [email protected]. ACDA then engages a Chartered Engineer to investigate, report and advise, and arranges for defects to be corrected.Equipment faults go to the manufacturer under its warranty, and your member can help you lodge that claim.

Before you sign

• Capacity is calculated by an approved method, not a rule of thumb.
• Every outlet, zone and control is listed, with where each goes.
• Power supply, plinth, drainage, pipe covers and rubbish removal are marked included or excluded.
• Removal of the old system is on the quote.
• Warranty period and recommended servicing frequency are written down.
• You have asked for an alternative if the first proposal is beyond your budget.

Every accredited member's quote already sets out each item above, so you know what you are paying for before you sign.