South Australia has the highest penetration of rooftop solar in the world and one of the most renewable-heavy grids of any jurisdiction, and it also has some of the highest retail electricity prices in the country. Both of those facts make energy efficiency work on an Adelaide home unusually worthwhile. A renovation is the cheapest possible moment to do it, because the walls are already open and the trades are already on site.
This guide covers what actually reduces energy use in an Adelaide house, what it costs, what returns it produces, and what assistance is available.
Why Adelaide Houses Perform Badly
The city’s housing stock has three characteristic problems.
- Solid masonry with no insulation. Stone and double brick walls have enormous thermal mass and essentially no thermal resistance. In a well-designed house that mass is an asset; in an uninsulated one it simply stores summer heat and releases it into the bedrooms at midnight.
- Leaky envelopes. Suspended timber floors with subfloor ventilation, unsealed chimneys, gaps around doors and windows, ceiling penetrations and unsealed exhaust fans. A typical pre-1980 Adelaide house exchanges its entire air volume many times an hour without anyone opening a window.
- Poor orientation and unshaded western glazing. Much of the post-war subdivision was laid out without regard to solar orientation, leaving large west-facing living room windows that turn a 38 degree afternoon into a 30 degree evening indoors.
The result is houses that are expensive to cool through a summer with regular 40-degree days and expensive to heat through a genuinely cold, wet winter.
The Upgrades, in Order of Return
1. Ceiling insulation
The single highest return available. Around a quarter to a third of unwanted heat transfer in an uninsulated Adelaide house happens through the ceiling.
- Cost: $2,000 to $4,500 for a typical house, retrofitted
- Specify R6.0 or better. The additional cost over the minimum is small and the performance difference is not.
- Ensure full coverage with no gaps, particularly around downlights, hatches and the perimeter over the top plate
- Where existing insulation is present but thin, compressed or displaced, top it up rather than assuming it is doing its job
2. Draught sealing
Cheap, unglamorous, and one of the largest measurable improvements in an old Adelaide house.
- Cost: $600 to $2,500 depending on how thorough
- Weather seals to external doors and windows
- Chimney balloons or dampers in unused fireplaces — an open chimney is a permanent hole in the roof
- Sealing gaps in floorboards, and around skirtings on suspended floors
- Sealed, self-closing exhaust fans and rangehood dampers
- Sealing service penetrations in the ceiling
- Sealed downlight covers, or replacing old downlights with sealed LED units
3. Roof colour and roof space ventilation
- A light roof colour at the next re-roof costs nothing extra and can keep the roof surface 20 to 25 degrees cooler on a 40 degree day
- Roof space ventilation — ridge vents, eave vents or whirlybirds — $600 to $2,500, and it directly reduces the evening heat load
4. External shading to west and north glazing
- Cost: $1,500 to $12,000 depending on the approach
- External shading stops heat before it enters. Internal blinds only reduce it after it has arrived.
- Fixed eaves or a pergola on the north; adjustable louvres, shutters or external blinds on the west
- Deciduous planting on the west and north-west, which is the cheapest option and takes several years
5. Wall and underfloor insulation
- Cavity brick walls can be injected with insulation — $3,000 to $8,000 — but only where the cavity is clean and dry. Never inject a wall with rising damp; it traps the moisture and makes the problem worse.
- Solid stone or single-skin masonry cannot be cavity-filled. The option is furring out and lining the internal face with a ventilated cavity, insulation and plasterboard, at $180 to $280 per square metre. Use vapour-permeable materials and maintain the cavity — sealing a damp stone wall is destructive.
- Underfloor insulation to suspended timber floors — $2,500 to $6,000 — while maintaining subfloor ventilation. Worthwhile in Adelaide’s cold winters.
6. Windows and glazing
- Double glazing: $900 to $1,800 per square metre installed for a full replacement. Effective in both seasons here, and it cuts noise, but it is well down the priority list because the cost per unit of benefit is higher than everything above.
- Secondary glazing — an internal panel over the existing window — $400 to $900 per square metre, delivers much of the benefit, retains original windows, and is usually acceptable in heritage areas.
- Low-E film on existing glass — $80 to $180 per square metre — reduces heat gain substantially on west-facing glass for a modest outlay.
- Heavy lined curtains with pelmets, which stop the convection loop down the cold glass. Genuinely effective and often overlooked.
7. Heating and cooling equipment
- Reverse-cycle air conditioning is the most efficient way to both heat and cool in Adelaide. Modern inverter units deliver three to five units of heat per unit of electricity.
- Size it after the envelope work, not before. An oversized unit short-cycles, runs inefficiently and controls poorly.
- Evaporative cooling suits Adelaide’s dry summer and costs far less to run than refrigerated cooling, but it needs open windows and struggles on the humid days. Many Adelaide homes run both systems.
- Zoning a ducted system so you condition the rooms in use rather than the whole house
- Ceiling fans throughout — cheap to install, almost free to run, and they raise the comfortable temperature by two to three degrees
- Replacing gas heating with a heat pump makes increasing economic sense as gas supply charges rise and the grid decarbonises
8. Hot water
Water heating is typically the second-largest energy use in an Adelaide home.
- Heat pump hot water: $3,500 to $6,500 installed before incentives, using roughly a quarter to a third of the energy of electric resistance heating
- Solar hot water with electric or gas boost: $4,000 to $8,000, and Adelaide’s solar resource is excellent
- Timing electric hot water to run in the middle of the day to soak up your own solar generation is one of the cheapest efficiency measures available if you already have panels
9. Solar and batteries
- Rooftop solar: $4,500 to $9,000 for a typical 6.6kW system after the federal small-scale scheme discount. Adelaide’s solar resource is among the best in the country.
- Batteries: $8,000 to $16,000 installed. The economics have improved as feed-in tariffs have fallen and evening prices have risen, and they improve further where the battery joins an approved virtual power plant.
- Do the efficiency work first. Generating power to run an uninsulated house is a more expensive way to reach the same comfort than insulating it.
Rebates and Assistance in South Australia
Retailer Energy Productivity Scheme
REPS is the main state mechanism. Energy retailers are required to deliver energy productivity activities to South Australian households and businesses, and they deliver them as discounted or free upgrades through approved providers. Activities available under the scheme include:
A related guide to consider while planning this work is Ceiling Insulation Upgrades: Top Up Existing Batts or Replace Them?.
- Home insulation and draught sealing upgrades
- Energy efficient lighting
- Water efficient shower heads
- High-efficiency air conditioning
- Water heating appliance upgrades, including heat pumps
- High-efficiency appliances such as freezers, clothes dryers and pool pumps
- Battery connections to approved virtual power plants
Two things are worth knowing. First, you do not have to be that retailer’s customer to access their energy saving activities. Second, different retailers offer different activities, so it is worth checking several rather than assuming your own retailer’s offer is the market. You cannot receive the same item twice for the same address.
Low-income households and other priority groups may qualify for additional discounts through REPS priority group referrals. The scheme is administered by the Essential Services Commission of South Australia, which handles complaints.
Other assistance
- Federal small-scale renewable energy scheme — the up-front discount applied to rooftop solar and solar or heat pump hot water through small-scale technology certificates
- Federal household battery support, which has substantially improved battery payback
- Concessions for eligible South Australian households on energy bills, administered by the state government
- Retailer-specific offers beyond the REPS minimum, which vary and change
- Programs change regularly — check current offers through the state Energy and Mining site and the federal energy.gov.au rebates listing before committing to any upgrade
What This Is Worth
A typical uninsulated, undraught-sealed Adelaide house spending $2,800 to $4,200 a year on energy can realistically reduce that by 40 to 60 per cent through envelope work, efficient equipment and solar, without any change to how the household lives.
Indicative paybacks
- Draught sealing: 1 to 3 years
- Ceiling insulation: 2 to 5 years
- Roof space ventilation: 3 to 6 years
- External shading: 3 to 8 years
- Heat pump hot water: 4 to 8 years, faster with REPS assistance
- Rooftop solar: 4 to 7 years
- Wall insulation: 8 to 15 years
- Double glazing: 15 to 25 years on energy savings alone — the comfort and noise benefits are the real justification
The comfort return is harder to quantify and often matters more. A house that stays below 26 degrees on a 40 degree day without the air conditioner labouring, and above 18 degrees on a July morning without heating overnight, is a different place to live.
Sequencing It Into a Renovation
The marginal cost of doing this work during a renovation is a fraction of doing it separately.
- Before construction: get an energy assessment of the existing house and model the improvements, so you are choosing on evidence rather than intuition
- During demolition: identify every accessible wall, floor and ceiling cavity
- While walls are open: insulate, seal penetrations, and run conduit for future solar, battery and EV charging even if you are not installing them yet
- Before linings go on: photograph the insulation and the sealing, because you will never see it again
- At roof works: upgrade ceiling insulation, add roof ventilation, and choose a light roof colour
- At fit-out: sealed LED downlights, efficient appliances, and correctly sized heating and cooling based on the improved envelope
- After completion: commission the systems properly and get the controls set up so the household actually uses them as designed
The Mistakes
- Buying equipment before fixing the envelope. A large air conditioner in a leaky house is an expensive way to keep the neighbourhood warm.
- Injecting cavity insulation into a damp wall. In Adelaide, with its widespread salt damp, this is a serious and expensive error. Resolve the damp first.
- Sealing a solid stone wall behind foil-faced insulation and plasterboard. The wall needs to breathe; trapping moisture in it drives the damp higher and destroys the fabric.
- Sealing a house tightly without providing ventilation. Draught sealing needs to be paired with controlled ventilation — properly ducted exhaust fans, and ideally a heat recovery system in a very tight house — or you get condensation and mould through the winter.
- Blocking subfloor vents while insulating underfloor. The subfloor must stay ventilated.
- Ignoring the west. No amount of insulation compensates for unshaded west-facing glass in an Adelaide summer.
- Assuming the rebate landscape is static. REPS activities and federal programs change; check before you buy, not after.
Done in the right order, an Adelaide house can go from one of the least comfortable housing types in the country to one of the most pleasant, because the climate is genuinely benign for eight months of the year and the building is what makes the other four difficult. For the material and orientation side of this, see renovating for the Adelaide climate.
Getting an Assessment Before You Spend
The most common way to waste money on home energy work is to buy the upgrade that is being marketed to you rather than the one your particular house needs. A house that is losing heat through an uninsulated ceiling and a dozen unsealed penetrations does not need double glazing; it needs $4,000 of insulation and sealing that will outperform $40,000 of windows.
What an assessment gives you
- A thermal image survey showing exactly where heat is entering and leaving — the gaps, the thermal bridges, the missing insulation, the failed seals. This is the single most useful diagnostic available and it typically costs $400 to $900.
- A blower door test quantifying the air leakage rate, which tells you whether draught sealing is your biggest opportunity or a minor one.
- A NatHERS or similar rating of the existing house, with modelled improvements so you can compare options on projected performance rather than on intuition.
- A prioritised list with costs and expected savings against each item.
Doing a rough version yourself
- Go into the roof space with a torch and look at the insulation — is it present, is it the full depth, is it displaced around downlights and the perimeter?
- On a windy day, hold a lit incense stick near door frames, window frames, skirtings, downlights, exhaust fans and the meter box penetration, and watch the smoke
- On a cold morning, touch the internal face of external walls and the underside of the ceiling — a big difference between them tells you where the loss is
- Note which rooms overheat and at what time of day, which identifies the glazing problem
- Check whether every chimney is sealed and whether exhaust fans have working dampers
All-Electric: Is It Worth It in South Australia?
South Australia’s grid carries a very high renewable share and continues to shift, while gas supply charges have risen faster than usage charges. That combination changes the arithmetic on gas appliances in a way that is more pronounced here than in most of the country.
A related guide to consider while planning this work is Replacing Your Hot Water System: Heat Pump, Solar, Gas or Electric?.
The case for going all-electric
- The daily gas supply charge disappears entirely once the last gas appliance is removed and the connection is abolished. On a household using little gas, that fixed charge can be most of the bill.
- Heat pumps deliver three to five units of heat per unit of electricity, against roughly 0.8 to 0.95 for gas appliances.
- Rooftop solar makes the marginal electricity very cheap, and Adelaide’s solar resource is excellent.
- Indoor air quality improves with the removal of unflued gas appliances and gas cooking.
- Induction cooking is faster, more controllable and easier to clean than gas, which most people who switch report within a fortnight.
What it costs and what to watch
- Heat pump hot water: $3,500 to $6,500 installed, often substantially reduced through REPS activities
- Induction cooktop plus the cookware: $1,500 to $5,000, plus a dedicated circuit
- Reverse-cycle to replace gas heating: $9,000 to $18,000 for ducted, less for split systems
- Switchboard and possibly supply upgrade: $1,200 to $4,000. Check the capacity before committing — this is the item that surprises people.
- Abolishing the gas connection has its own fee, and it must be the last step
Do it during a renovation if you can, because the circuits, the switchboard and the appliance positions are all being touched anyway and the marginal cost is a fraction of doing it as a standalone project.