Do curtains save energy? What whole-house modelling shows for Australian homes

Yes, and the size of the saving depends on where you live and how the curtain gets used. Fitting blockout curtains to every window of a representative Australian home saves 5% of total heating and cooling energy cost in Hobart, 9% in Melbourne, 11% in Sydney and 17% in Perth. Set the same curtains to open and close on a schedule instead of by hand and Brisbane's figure reaches 34%. Every number in this guide is a modelled estimate for a representative home, not a measurement of a specific house.

We can publish that because the industry body provides whole-house energy modelling on official WSAA data to its members, and we ran the same house through all eight capital cities on it. If you want the figure for your own postcode and the covering you are actually considering, the energy savings calculator runs it live.

A thermal curtain is a label, not a category

Search for thermal curtains and you will find plenty of products sold under the name. What you will not find is a rating behind it. Per-range thermal ratings do not exist for curtain fabrics in Australia unless a fabric has been specifically developed and tested as a thermal product. So mostly, a thermal curtain is a description of intent, not a measured performance class. If a supplier quotes you a thermal number for a particular fabric range, ask where it came from.

What can be modelled is the class of covering. A blockout curtain, a sheer curtain, an uncoated curtain: those are the units the modelling works in. It is why every figure below describes a category and a fabric type rather than a range you can put in a cart. That is the honest limit of what anyone in this market can currently tell you.

Modelled savings in eight capitals

The table runs one house in all eight capitals. Everything except the postcode stays fixed: single storey, brick veneer, built between 2010 and 2021, single glazed, electrically heated, with a blockout curtain face fitted to every window and no pelmet. Blockout is spelled blackout in a good share of Australian searches, and it is the same fabric either way.

Under manual operation Perth leads at 17%, then Adelaide at 12%, Sydney at 11% and Brisbane at 10%. Melbourne comes in at 9%, Darwin at 8%, Canberra at 7% and Hobart at 5%. Those are total energy cost savings across the whole year, heating and cooling together.

The headline percentage hides the more useful result, which is that the same curtain is doing a completely different job in each city. Melbourne is a summer story: 22% off summer cooling against 6% off winter heating. Brisbane under manual operation runs the other way, 14% off winter heating against 9% off cooling. Canberra saves 35% of summer cooling and 5% of winter heating. Darwin has no winter heating figure at all, because the model does not heat a Darwin house.

Read those seasonal figures carefully, because each one is a share of that season's own energy cost and not of the whole bill. Hobart saves 42% of its summer cooling and 5% overall, because a Hobart house barely cools in the first place.

Manual against automated, and the result that surprised us

The model reports every scenario twice, once for a covering somebody opens and closes by hand and once for a covering that follows an operating schedule. The gap between those two runs is the largest effect in the whole dataset, and it points in an unexpected direction.

Summer cooling roughly doubles or triples. Sydney goes from 16% to 56%. Perth goes from 26% to 56%. Brisbane goes from 9% to 38%, and Canberra from 35% to 72%. Hobart is the exception, where summer sits at 42% either way.

Winter heating stays flat or edges down: Sydney 9% to 7%, Adelaide 7% to 5%, Perth 9% to 7%, Melbourne 6% to 6%, Hobart 5% to 5%.

The modelling reports the outcome and not the reason, and we are not going to invent one. What it does state is that the automated figures assume the covering follows the modelled operating schedule. That is the practical point for anyone weighing up motorised curtain tracks. The schedule is the thing being paid for. A curtain only delivers the automated number on the days someone is home to work it, and a track on a timer is home every day.

Why Melbourne saves more carbon than Sydney

Melbourne's modelled house saves 114 kg of CO2 a year. Sydney's saves 49 kg. Melbourne does that on a 9% saving while Sydney is on 11%, so the smaller percentage saves more than twice the carbon. Darwin goes further again, 208 kg a year on an 8% saving, rising to 677 kg once the covering runs on a schedule.

The percentage tells you how much less energy the house uses. The kilograms tell you what that energy was made of. If carbon is the reason you are reading this, the grid your house is plugged into moves the answer more than the curtain does. That is not a comfortable thing for a curtain maker to publish, and it is what the data says.

The result follows the fabric class, not the product name

We ran every covering we sell through the same Perth house, and the grouping is worth knowing before anyone shops on energy alone. The model works by fabric class and mount position rather than by product name. A blockout curtain, a blockout roller blind, a roman blind, a venetian and a vertical all return the same 17% manual and 30% automated. A sheer curtain and a sunscreen roller both return 13% and 21%. An uncoated curtain sits between them at 15% and 28%.

Two categories model higher than any of those. Honeycomb blinds come in at 22% manual and 36% automated, and plantation-style PVC shutters at 24% and 39%. We would rather tell you that than have you find it somewhere else. Energy performance is one input into a window covering decision, and rarely the deciding one. If it is the only thing you are buying on, the modelling does not put curtains at the top.

Double curtains, and what the modelling cannot say

A double curtain hangs a sheer and a blockout on one double track, and it is the configuration we make most often for living rooms and bedrooms. The modelling has no way to describe it. Each run puts a single covering on the window, so there is no combined figure for a sheer and a blockout together, and nobody should publish one.

What you can take from it is narrower and still useful. The blockout layer's figure is the one that applies, because the blockout is the layer you close when you want the thermal effect. A sheer on its own models at 13% manual and 21% automated in Perth, so the daytime layer is not doing nothing. Adding the two numbers together, though, is not how any of this works, and if you see double curtains sold on a stacked energy figure, that figure is invented.

How the modelling works, and what it does not measure

Every figure here comes from whole-house modelling on official data from the Window Shading Association of Australia (WSAA). The scenario is fixed: single-storey brick veneer built between 2010 and 2021, single glazing, electric heating, the covering fitted to every window, face fit with no pelmet, light street-side appearance. Only the postcode and the covering change between runs.

The model estimates from the typical insulating and optical performance of the specified class of product. It is indicative. It is not an assessment of the energy efficiency or thermal characteristics of any specific house, including yours. Orientation, insulation, glazing, the climate zone you sit in within your state and your own habits all move the real number, and none of them are in here.

Three limits are worth stating plainly rather than in a footnote. Automated results depend on the covering following the modelled operating schedule, so a motor you override every morning gives you the manual number. The model reports at the level of product category and fabric type, so it cannot say that one blockout range outperforms another. And a percentage saving on heating and cooling is not a percentage off your bill, because heating and cooling is only part of what a house uses.

Where to start

Run your own postcode through the energy savings calculator. It takes the same modelling, applies it to the city and the covering you are actually considering, and shows the manual and automated results side by side with the same caveat attached.

One thing worth separating out, because it is easy to blur. We sew our curtains and build our curtain tracks, motorised tracks included, in our own factory in Western Australia. That is a manufacturing fact and it is not an energy claim. The modelling describes a category of window covering and knows nothing about where it was made.

Then order the fabric before you order the curtains. Sample packs come with free express post, so you can hold the swatches up in your own room before you commit. Light behaves differently there than it does on a screen, and no amount of modelling settles that part for you.