Do curtains actually save you money on energy bills? I went looking for the numbers

In partnership with Curtain & Blind Co.

Every time I mention curtains in a build or reno, someone in the comments asks the same thing: do curtains actually make a difference to your energy bill, or is ‘thermal curtains’ just a label a curtain company wants you to believe?

Fair question. I wanted an actual answer, not a vibe, so I went digging into some independent simulation data from the Window Shading Association of Australia, modelled specifically for homes in Melbourne and Sydney. And honestly, the numbers surprised me a bit.

First, what house are we even talking about?

The modelling was run on a single storey brick veneer home built between 2010 and 2021, single glazing, electric heating. So basically a very normal, very common Aussie home, not some architect’s dream with triple glazing and mud brick walls. The curtain in the model was a face-fit blackout curtain with no pelmet, covering the whole house. Nothing fancy, just a standard setup, which honestly makes the results more useful because it’s realistic.

They compared two ways of living with your curtains: manual, where you open and close them whenever you remember (so, let’s be honest, not always at the ideal time), and automated, where they’re opened and closed on a schedule that actually matches the weather.

Melbourne: the summer numbers are wild

For a Melbourne home, here’s what the modelling found:

• Total energy cost savings: 10% a year if you’re doing it manually, 13% if it’s automated
• CO2 saved: 114 kg a year manual, 158 kg automated
• Summer aircon cost savings: 23% manual, 45% automated (yep, basically doubles)
• Summer aircon energy savings: 59 kWh manual, 116 kWh automated
• Winter heating cost savings: 7% manual, 6% automated
• Winter heating energy savings: 75 kWh manual, 70 kWh automated

The bit that jumped out at me is summer. Just by timing your curtains properly instead of whenever you think of it, you nearly double your aircon savings. Winter’s a bit different, manual and automated are close, which makes sense when you think about it, most of us are already pretty good at shutting curtains on a freezing morning without needing a schedule to remind us.

Sydney: automation makes an even bigger difference

Same house, same curtain, this time modelled for Sydney:

• Total energy cost savings: 11% manual, 20% automated
• CO2 saved: 49 kg a year manual, 92 kg automated
• Summer aircon cost savings: 16% manual, 56% automated
• Summer aircon energy savings: 24 kWh manual, 85 kWh automated
• Winter heating cost savings: 10% manual, 8% automated
• Winter heating energy savings: 44 kWh manual, 36 kWh automated

That summer jump for Sydney is honestly the biggest swing in either city. Getting the timing right more than triples the cooling savings compared to just winging it. So to answer the question everyone keeps asking me: yes, curtains save energy, but a lot of the saving comes down to when you close them, not just what fabric you picked.

Why “layered” curtains keep coming up

This is where double layer curtains, or layered curtains as some people call them, start to make a lot of sense. A single blackout layer is great at blocking heat and light, but it’s a bit all-or-nothing. Pair it with a sheer or secondary layer and you get way more flexibility, you can filter light and let some airflow through without fully exposing the room to outside temperatures. Given how differently Melbourne and Sydney behave across seasons in this data, that flexibility is honestly worth thinking about, especially if your place gets proper cold mornings and stinking hot afternoons in the same week (looking at you, Melbourne).

What actually makes thermal curtains work

If you’re curtain shopping and want them to genuinely perform as insulating curtains and not just look nice, here’s what I’d be checking:

1. Fabric weight and weave. A real blackout curtains energy saving effect comes from a dense, tightly woven fabric, not just something that looks dark.
2. Fit. Gaps at the top, sides or floor let all that conditioned air sneak straight past the curtain, no matter how good the fabric is.
3. Mount position and width. Curtains hung close to the window and wide enough to fully cover the frame will always outperform a narrow, decorative hang.

Also worth knowing, a lot of curtains sold online in Australia are actually from resellers rebadging imported stock rather than businesses making the product themselves. Curtain & Blind Co. makes their curtains, and the tracks that hang them, in their own factory here in Australia, something they’ve been doing for over 50 years. That matters more than you’d think, because it means your curtains and blinds can be made completely custom to your actual window sizes instead of a generic off-the-shelf width that never quite fits.

Try before you commit

Fabric weight is genuinely hard to judge from a product photo on a screen, so it’s worth getting your hands on a swatch first. Curtain & Blind Co.’s sample service ships express for free, and you get a $10 voucher off your order if you decide to go ahead, so there’s a pretty low-effort way to feel how a blackout fabric actually hangs and drapes before committing to full curtains, blinds or shutters. They ship Australia wide too.

You can have a browse of the full blackout curtains range here: Curtain & Blind Co. blackout curtains

This post was created in partnership with Curtain & Blind Co. Energy savings figures are drawn from Window Shading Association of Australia simulation modelling for single storey, single-glazed brick veneer homes built between 2010 and 2021, and are indicative estimates rather than an assessment of any individual property.