Most people manage summer heat from the inside. The blinds come down at eleven, the curtains get pulled across the western windows by three, and the air conditioner runs anyway.
It works, more or less. What it does not do is stop the heat arriving. By the time you are drawing an indoor blind, the sun has already passed through the glass and turned into heat inside the room. The blind is now absorbing that heat and radiating a fair share of it straight back at you.
Shading the outside of the glass is a different proposition, and the difference in performance is larger than most homeowners expect.
Where the heat actually gets in
Sunlight hitting a window arrives as shortwave radiation. Glass lets most of it through. Once inside, it strikes floors, walls and furniture, which absorb it and re-emit it as longwave heat. Glass is much worse at letting that back out, so it stays in the room.
An internal blind sits on the wrong side of the glass for this. It intercepts the light after it has already entered, so a portion of the energy is trapped between the fabric and the window and ends up in the room regardless.
An external shade stops the radiation before it reaches the glass. Whatever heat the fabric absorbs is released into open air outside, where it does not matter.
Industry testing consistently shows external shading blocking the large majority of solar heat gain, against a much smaller share for internal blinds of similar fabric. Homeowners tend to notice the difference within one hot afternoon.
The options, briefly
Folding arm awnings. A fabric awning that projects out from the wall on hinged arms, usually over a deck, patio or a run of glass doors. Retracts fully when not needed. The main choice for shading an outdoor living area rather than a single window.
Pivot arm awnings. Angled outwards from the top of a window, with arms that swing down. Better suited to individual windows and to walls where there is nothing below to project over.
Drop down awnings and zip screens. Drop vertically down the face of the opening. Zip screens run in side tracks, which keeps them stable in wind and makes them a practical way to close in a balcony or an alfresco area for most of the year.
External venetian blinds. Adjustable metal slats mounted outside the window. Expensive relative to the others, but the only option that lets you block direct sun while keeping the view and the daylight.
Matching the option to the aspect
The direction a window faces should drive the decision more than the look.
North facing. The sun sits high in summer and low in winter. A fixed or projecting shade above the window can cut the summer sun while still letting the low winter sun through, which is exactly what you want. Retractable awnings suit north walls well.
West facing. The hardest orientation in Australia. Late afternoon sun arrives at a low angle and comes in almost horizontally, so an overhead shade does very little. You need something that drops down the face of the glass, which is where zip screens and drop down awnings earn their place.
East facing. Same problem as west but in the morning, when it is less objectionable because the house has not yet heated up. Often manageable with internal coverings alone.
South facing. Minimal direct sun in most of the country. Usually not worth external shading.
Getting this wrong is common. Plenty of homes end up with folding arm awnings over a west facing deck, where they shade the paving beautifully at midday and do nothing at all at five in the afternoon when the heat is worst. The fix is usually a drop down screen at the front edge, used together with the awning.
Practical considerations before you commit
Wind. Fabric awnings have wind ratings, and exceeding them is how arms get bent. Anywhere coastal, ask directly what the rating is and whether a wind sensor is included with motorised units. Zip screens in tracks handle wind better than open awnings.
Fixing. The awning is only as good as what it is bolted to. Brick and concrete are straightforward. Rendered walls, cladding, and older timber framing need the fixing points checked before install, not after.
Body corporate and council. Apartments almost always require owners corporation approval for anything fitted to the exterior, and many buildings specify a colour. Freestanding homes rarely need council approval for a retractable awning, but heritage listings and some overlays are exceptions worth confirming.
Motorisation. Worth it on anything you will use daily, and worth it on anything above head height. Manual crank handles are fine in theory and quietly stop being used within a season.
The payback
External shading is more expensive than an internal blind, and there is no getting around that. What you are buying is a reduction in the load your cooling has to work against, plus usable outdoor space through the hottest part of the year.
For a west facing room that currently runs the air conditioner from two until eight every summer day, the numbers make themselves.