Replacing an old wood heater: what to know before you buy

The firebricks have been crumbling for two winters. The door seal stops sealing partway through a burn. The glass blackens within an hour even with dry, well-seasoned hardwood. You've nursed the heater through another season, but you know the conversation is coming: do you keep patching this thing up, or is it time for a new wood heater?

If you're at that point, you've already done the hard part. You know wood heat works for your home. You know what it costs to run, and you know what kind of warmth you're not willing to give up. The decision in front of you is narrower than the first one was: whether your current heater has years of life left or is genuinely at end of life, what's changed in the wood heater market since yours was built, and what a replacement involves once you commit.

This guide walks through how to tell the difference, what current standards require, what the process looks like, and what it'll cost.

Signs your wood heater is at end of life

A well-built wood heater that's been looked after can run for 15 to 20 years. After that, the components that take the heat start to give up, and the cost of keeping it going can outpace the cost of starting fresh. Here's what to watch for.

• Crumbling or missing firebricks. Common after 10 to 15 years of regular use. Firebricks are replaceable on most units, and a single broken brick is a maintenance job. If most of the bricks are degraded and the steel behind them is showing heat damage, the firebox is past its useful life.
• Warped or cracked baffle plates. The baffle is what makes secondary combustion work. Replaceable on many models, but warping is a sign of sustained over-firing or a baffle that's reached the end of its service life.
• A door seal that won't hold. If you've replaced the rope seal once and it's failing again within a year, the door itself or the frame is likely warped. Glass blackening, smoke escaping at the door, and a fire that's hard to control all point here.
• A cracked or damaged firebox. Structural and not repairable. Replacement is the only safe option.
• Less heat from the same wood load. If a full firebox of seasoned hardwood doesn't warm the room the way it used to, internal degradation is usually the cause. Air leaks, baffle damage, and worn seals all rob heat output.
• A clean burn that won't stay clean. Glass that fouls within an hour of lighting, even with dry wood, usually means secondary combustion has stopped working. That points to the baffle, air supply, or combustion chamber no longer doing its job.

When you're not sure, have a wood heater technician look at it. Some of these signs are repairs you can have done in a morning. Others are the heater telling you it's done.

What's changed since your old wood heater was built

If your heater predates 2019, the rules it was built to are different to the rules a new heater is built to today. The current Australian Standard is AS/NZS 4013:2014, which applies to all new wood heaters sold in Australia from 8 August 2019. The standard sets a maximum of 1.5 grams of particulate emissions per kilogram of wood burnt and a minimum efficiency of 60 percent. [VERIFY WITH CLIENT: a draft revision, AS/NZS 4013:2024, was circulated for public comment in late 2024 but had not been finalised at the time of writing. Worth confirming the current state at publication.]

In practical terms, a heater built before 2019 will generally emit more particulates per kilogram of wood and burn more wood for the same heat output. Step back further to a unit built before 2010 and the gap widens. Combustion-chamber design, baffle technology, and air management have moved on significantly in the past 15 years.

The features that weren't standard a decade ago are now the baseline on Australian-made units that comply with the current standard:

• Secondary combustion that burns off particulates which would otherwise go up the flue, producing a cleaner burn and squeezing more heat out of the same wood load.
• Better firebricks and baffle design that hold heat in the firebox and direct it into the room.
• Larger glass viewing areas with door-wash systems that keep the glass clean during normal use.
• Improved door seals and air controls that give you finer control over the burn.
• More efficient flue systems including double-skinned and insulated options.
• A wider range of heat outputs so you can match the heater to the space rather than under- or over-sizing it.

Local council restrictions are another change worth knowing about. Some Victorian council areas, particularly those with air quality monitoring, have introduced restrictions on new wood heater installations or specific flue requirements. Existing units are usually grandfathered, but a replacement counts as a new installation. Check with your local council before you commit. Restrictions vary widely and change.

Sizing your replacement: don't assume the old size is still right

Most homeowners replacing a wood heater default to thinking that a 15kW heater needs to be replaced with another 15kW heater. It's the most common sizing mistake we see in the showroom.

A few things to consider before you settle on heat output:

• Has the home been re-insulated, double-glazed, or extended since the old heater was installed? Modern insulation and glazing can cut heat loss substantially. The room that needed 15kW in 2008 might need 10kW today.
• Modern heaters at the same nominal output deliver more usable heat. Higher efficiency means more of the energy in the wood ends up in the room rather than going up the flue.
• Open-plan renovations change the equation. If you've knocked through a wall since the old heater went in, the new heater has to warm the whole connected space rather than the original room alone.
• A working rule of thumb: 1kW of output heats roughly 10 square metres of well-insulated, single-storey space, or about 7 square metres of older, draughtier, or open-plan space. That gives you a starting point. The showroom team will run the numbers properly when you bring in the room dimensions.

Bring the room measurements, ceiling height, insulation upgrades, and any window changes when you visit. The team will recommend a unit from the Spectre, Supreme, Elite, or Radiant range that fits the space rather than overheats it.

What replacement involves

Replacement is more than swapping one box for another. Here's what the job covers from the day you order to the day you light the first fire.

Removal of the old unit. Most wood heaters weigh between 100 and 250 kilograms. Disassembly may be needed to get it out through doorways and around corners. Two installers and proper lifting equipment are standard. [VERIFY WITH CLIENT: whether Ultimate's installers handle removal and disposal as part of the replacement service, or whether this is the homeowner's responsibility to arrange.]

Flue assessment. Your old flue might be reusable. Stainless steel flues from a reasonably modern installation (post-2010) often pass inspection and can be retained, which is a meaningful saving. Older galvanised flues are usually replaced. Either way, the flue must comply with AS/NZS 2918:2018 for the new unit.

Hearth assessment. Modern heaters have specific hearth dimension and thickness requirements that may differ from your old unit's. In some homes, the existing hearth works fine. In others, it needs to be extended forward or replaced. The installer will measure during the site assessment.

Clearance assessment. The new heater's clearance to combustibles will likely differ from the old unit's. Modern double-skin freestanding heaters typically have lower clearance requirements than older single-skin designs, so the constraint is often easier than it sounds. The installer confirms this against the manufacturer's specifications.

Installation by a licensed installer under AS/NZS 2918:2018. Wood heater installation is regulated work and not a DIY job. The standard sets out the requirements for clearances, hearth construction, flue routing, weather flashings, and termination heights. A licensed installer signs off the work.

Disposal of the old unit. Most installers will take it away. Some councils accept old heaters at transfer stations for a fee. Scrap metal value covers the trip but not much more.

What it will cost

Honest pricing first, detail second. A new mid-range Australian-made wood heater sits in the $2,500 to $5,000 range. Removal of the old unit and disposal typically runs $200 to $500. A new flue, if required, costs $1,000 to $2,500 depending on whether it's a single or double-storey installation and how complex the routing is. Reusing an existing compliant flue saves a significant chunk of that figure.

Total replacement cost typically lands between $3,500 and $8,000 fitted, depending on which unit you choose and how much of the existing infrastructure can be retained.

The harder question is how that compares to repair. Here's how the maths usually works out:

Scenario	Approximate cost	When it makes sense
Replace door seal only	$80-$150	Heater under 10 years old, otherwise sound
Replace firebrick set	$250-$500	Bricks degraded but firebox sound
Replace baffle plate	$200-$450	Baffle warped, secondary combustion failing
Major repair (firebox, flue, baffle, bricks)	$1,500-$3,500	Multiple components failing on a heater 10 to 15 years old
Full replacement (new heater plus install)	$3,500-$8,000	Heater 15+ years old, pre-2019, or showing structural damage

If your heater is more than 15 years old, the maths often favours replacement. You can spend $2,000 to keep an old unit running for another three or four years, or $5,000 to put in a new heater that will run for 15 to 20.

Buying factory-direct from Ultimate Fires takes the retailer markup out of the new-unit cost, and every Ultimate firebox is backed by a 10-year warranty. Both are worth factoring into the value calculation alongside the install cost. For a deeper breakdown of installation costs, see our recent article on how much it costs to install a wood heater in Australia.

When repair beats replacement

Repair is the right call more often than the wood heater industry will admit.

If the heater is under 10 years old, complies with current emissions standards (look for the AS/NZS 4013:2014 plate inside the firebox or on the rear), and has a single failed component, repair is usually the smarter spend. Door seals, firebrick sets, baffles, and even glass panels are designed to be replaceable. A good wood heater technician can have most of these jobs done inside a day.

Replacement makes more financial and environmental sense when:

• The heater predates 2019 and is missing the AS/NZS 4013:2014 compliance plate.
• Two or more major components have failed at the same time.
• The firebox itself is cracked, warped, or showing structural damage.
• You're renovating, opening up the floor plan, or improving insulation in ways that will change the heat output you need.

If you're not sure which side of the line you're on, get a technician's opinion before you commit either way. The cost of a service call is small compared to the cost of repairing a heater that should have been replaced, or replacing one that had years of life left.

Book the changeover before winter

Wood heater installers get busy from late autumn onwards. By the time the first cold snap hits, lead times for a removal and replacement can stretch by weeks. The most practical move is to book the changeover in autumn or early winter, when installers have availability and you're not trying to time a heatless week around a Melbourne cold front.

If you're weighing it up now, the showroom team can do most of the assessment before a site visit. Bring photos of the existing heater (front, side, and the flue penetration through the ceiling), measurements of the room and the install location, and any details you have about the existing flue. Between that and a brief conversation about how the old unit has been performing, the team can usually advise on compatibility, flue reuse, sizing, and which model from the range fits best.

Ultimate Fires has showrooms in Dandenong South, Epping, Geelong, Ballarat, Adelaide, and Perth. Find your nearest one and we'll work the changeover through with you.