Is Your Roof Suitable for Solar? The 5-Minute Assessment

Most Australian homes have a roof that is genuinely suitable for solar — but "suitable" doesn't always mean "ideal." In about five minutes, you can assess whether your roof orientation, pitch, age, structure and shading make solar a strong investment, a marginal one, or one worth waiting on. For Wollongong and Illawarra homes, the bar is fortunately low: even east-west split roofs with mild escarpment shade typically generate enough power to pay back in 5–7 years.

The 5-minute self-assessment: what to check

You don't need a drone, a ladder or a structural engineer to do a first-pass assessment. With a free app like Google Maps satellite view, a rough idea of your roof's compass orientation, and a quick walk-around outside the house, you can get 90% of the way to a good answer.

Here are the five things to check, in order:

1. Roof orientation: north is best, but east-west works fine

In the southern hemisphere, north-facing panels generate the most energy across the year — typically 5–8% more than east or west, and 20–25% more than south.

But here's the underrated truth: east and west roofs are almost always still worth it. A north-facing 6.6kW system in Wollongong might generate 9,500 kWh/year. The same system split east-west would generate 8,800 kWh/year. The difference is roughly $180/year — meaningful but not deal-breaking, especially since east-west systems often align better with morning and evening household consumption.

What you should actually avoid: panels facing more than 20° away from due south. South-facing solar in NSW produces about 25–30% less than north, and the morning/evening generation curve doesn't match home use well. If your only available roof is south-facing, the maths is harder but not impossible — usually we'd recommend a slightly bigger system to compensate.

How to check orientation in 30 seconds

Open Google Maps on your phone. Find your house in satellite view. The little compass icon in the corner shows north — once you align it, you can see immediately which roof faces are northerly, easterly, etc. For Wollongong homes, the escarpment runs roughly north-south, which means most streets in the eastern suburbs (Towradgi, Corrimal, Bulli, Thirroul) have one roof face genuinely north or near-north.

2. Roof pitch: 15° to 30° is the sweet spot

Roof pitch (the angle of slope) affects how directly sunlight hits your panels across the year. For NSW latitudes (around 34°S in Wollongong), the optimum tilt is roughly 25–30°. Most modern Australian homes are built with roof pitches of 15–25°, which is close enough — typical losses from non-ideal pitch are 1–4%.

Flat roofs (under 5°) need tilt frames to angle the panels properly, which adds $400–$1,200 to the install cost but enables full output. Very steep pitches (35°+) also work fine, though installer access can be more complex.

The exception: low-pitch roofs (under 10°) with no tilt frames suffer more from dust and pollen build-up, especially in coastal areas like the Illawarra where salt and bird droppings accumulate. Tilted panels self-clean in the rain; near-flat panels need an annual hose-off.

3. Available roof area: how much can you actually fit?

A modern 440W solar panel measures about 1.7m × 1.1m. For a 6.6kW system you need around 15 panels and 28m² of contiguous roof area. For 10kW you need 24 panels and roughly 45m². For 13kW (the max under most NSW single-phase rules) you're at 30 panels and about 55m².

Most Illawarra homes have plenty of roof area on the main rectangular section over the living areas — the trickier bit is fitting around skylights, vents, hot water systems, antennas, dormers and chimneys. A good installer will design around these obstructions and may suggest moving the hot water unit or removing a redundant TV antenna.

Quick area estimate

Roof area on satellite view ≈ 100m². Subtract about 40% for setbacks, ridges, valleys and obstructions (in Wollongong we typically get usable area of around 60% of total roof footprint). So a 100m² roof realistically gives you 60m² of usable area — easily enough for 13kW.

4. Roof structure and condition: the most overlooked factor

Solar panels last 25–30 years. Your roof needs to last at least that long without needing replacement. If your tiles are cracked, your colorbond is faded and rust-pocked, or your roof is approaching 25 years old, the right move is usually to re-roof first (or at least re-roof the panel area), then install solar.

Removing and re-installing solar panels later costs $1,500–$3,500 — money you don't want to pay. If your roof has 5–10 years of life left, a re-roof now plus solar is the cheaper long-term path.

Roof types and how they affect solar:

Colorbond / metal: Best for solar. Easy to fix mounting brackets, lasts 40+ years, no breakage risk. Most modern Wollongong homes are colorbond.

Concrete tile: Standard for older Illawarra homes. Easy to install on with proper hooks. Tiles can be brittle when walked on; a good installer minimises traffic.

Terracotta tile: Can be installed on but more breakage risk. Older terracotta (40+ years) is sometimes too brittle and may need replacement first.

Asbestos cement (older homes pre-1985): Cannot have solar installed without licensed asbestos removal first. If your roof is fibrous cement and pre-1985, get an asbestos audit before going further.

Slate: Rare in NSW but possible. Specialist installers only.

5. Shading: the quiet killer of solar performance

A single shaded panel can drag down output across an entire string. For a typical Illawarra home, the shade culprits are:

Trees — especially large eucalypts, established jacarandas and the older fig trees common around Coniston, North Wollongong and Bulli. Trees grow, so the shade situation in 5 years is usually worse than today. Check whether trimming or removal is acceptable to you and the council before committing.

Neighbours' buildings — a two-storey house immediately north of a single-storey home will shade portions of the roof from late afternoon onwards in winter.

The escarpment itself — homes in Mt Pleasant, Mount Ousley, Figtree and parts of Unanderra get late-afternoon escarpment shade in winter. Generation drops by about 15–25% in winter months for affected properties, recovering in summer.

Chimneys, antennas, hot water units — small but persistent shade sources that good system design routes around.

The good news: shading no longer disqualifies a roof. Microinverters and DC optimisers (Enphase, SolarEdge, Tigo) isolate each panel's performance. A shaded panel only reduces output from that one panel — not the whole array. We've seen Wollongong homes with significant tree shade still produce 80–90% of an unshaded equivalent thanks to good optimisation.

Use our free Solar Savings Calculator to see your personalised payback period.

Special cases: heritage homes, strata and unusual roofs

Heritage and conservation areas

Parts of inner Wollongong, Kiama and Berry sit within heritage conservation areas where solar may need a Development Application rather than going under exempt development rules. The local council planning department can confirm in 10 minutes whether your address is affected. If it is, dark-on-dark panels positioned away from the street view usually pass council review.

Strata and townhouses

If you live in a strata complex, you'll need owners corporation approval to install solar on common roof areas. Some strata schemes have already adopted solar policies; many haven't. Start the conversation early — approval can take 2–6 months. NSW law has been pushing strata schemes toward easier approval, and the Cheaper Home Batteries Program now includes strata-friendly options.

Unusual roofs (curved, glass, very small)

Curved roofs need flexible panel solutions or creative racking. Glass conservatory roofs can have semi-transparent panels but at higher cost. If you have less than 20m² of usable area, a system smaller than 4kW may not be financially worth installing — but a heat pump hot water system or smaller plug-in solar may be a better fit.

When you should fix something before installing solar

Don't install solar before fixing these issues:

1. A roof leak or damaged tiles — solar mounting cannot be installed safely on damaged roofing.

2. A roof more than 20 years old without recent inspection — re-roof first.

3. Asbestos roofing (typically pre-1985 fibrous cement) — replace or encapsulate first.

4. Significant tree shade you're not willing to address — get an honest estimate of the performance hit before committing.

5. Pending major renovations that affect the roof (extensions, dormers) — finish those first.

Frequently Asked Questions

My roof faces south. Should I forget about solar?

Not necessarily. South-facing solar in Wollongong produces about 70–75% of north-facing output. That's still meaningful — and if you have available east or west area, a split-orientation system can be very competitive. We'd typically recommend either accepting the lower output or up-sizing the system to compensate.

How do I know if my roof can support the weight?

Modern panels weigh about 12kg/m² installed. Australian residential roofs are designed to comfortably handle this — a CEC-accredited installer will assess structural suitability during the on-site survey. The only common exception is older terracotta tiles or some skillion roofs with light truss work, which may need engineer sign-off.

Will my roof need a Development Application from Wollongong City Council?

Most solar installs in NSW fall under "exempt development" — meaning no council DA is required. The exception is heritage-listed properties or homes in heritage conservation areas. Coastal Solar Co. handles this check as part of every quote.

Is a flat roof a problem?

No, but you'll need tilt frames. Tilt frames angle panels at the optimal pitch (around 20–25°) and add about $400–$1,200 to the install cost. They also reduce wind-loading concerns on flat roofs. Many Illawarra commercial buildings have flat-roof solar arrays running for years.

My roof is 18 years old. Should I wait?

Probably not. A well-maintained colorbond roof at 18 years has another 20+ years of life. A concrete-tile roof at 18 years is also typically fine. The age threshold to worry about is 25+ years for colorbond and 35+ for concrete tile. If in doubt, get a roofer to inspect — most will do a free quick check.

What's the most common roof issue you find on Illawarra homes?

Honestly, it's salt-related rust around skylight flashings and gutter junctions on coastal homes (Austinmer, Bulli, Wombarra). It's almost never a deal-breaker — but it's worth fixing or replacing the affected flashing before solar goes on, because solar contractors won't be the ones repairing it later.

Ready to get your personalised quote? Contact our CEC-accredited team — we'll call you back within 5 minutes.