Hot-Dip Galvanized Steel vs Aluminum Solar Mounting: The Full Comparison

Almost every solar mounting quotation comes down to one question: steel or aluminum? This comparison gives you the numbers behind the choice, and the specific conditions where one clearly beats the other.

The two materials at a glance

Cost: steel wins at scale

On a per-kilowatt basis, HDG steel ground mounts are typically 30–50% cheaper than aluminum equivalents for arrays above 500 kW. The gap narrows for small rooftop systems because aluminum profiles are lighter to ship and easier to handle on a roof, but for any structure where strength matters — long purlin spans, high wind zones, carports — steel delivers more load capacity per dollar.

Corrosion: aluminum is not automatically better

A common myth is that aluminum "never corrodes". In fact, aluminum is vulnerable to galvanic corrosion when in direct contact with steel or copper hardware — which is why stainless steel fasteners are mandatory — and to pitting in aggressive coastal chloride environments. Properly galvanized steel (85 μm per ISO 1461) has a proven 25-year outdoor track record worldwide, and for truly harsh coastal sites, duplex systems (galvanizing + powder coat) outperform bare anodized aluminum.

Strength and deflection: steel is stiffer

Young’s modulus of steel (~210 GPa) is three times that of aluminum (~70 GPa). For the same profile geometry, steel deflects one-third as much under wind and snow. Designers compensate in aluminum by increasing section depth — which erodes the weight advantage. For carport spans of 5–6 m, steel columns and beams are the engineering default.

When aluminum is the right choice

• ▸Residential and light commercial rooftops where weight on the roof structure is the binding constraint
• ▸Flat roof ballast systems (non-penetrating) where you want to avoid heavy steel
• ▸Coastal rooftops with high chloride exposure, using anodized 6005-T5 and SS304/316 hardware
• ▸Installations on lightweight metal roofs that cannot take point loads

When galvanized steel is the right choice

• ▸Utility-scale ground mounts of any size
• ▸Solar carports and elevated structures
• ▸High wind or snow regions (member strength matters)
• ▸Agri-PV structures spanning over crops
• ▸Any project where budget per watt is a priority

The hybrid answer

Many commercial projects use a hybrid: galvanized steel for the main structure (posts, beams, purlins) and aluminum or stainless for the panel-level clamps and rails. This captures steel’s strength where loads are highest and light materials where handling matters. Ask your supplier for a hybrid quotation if you are in the 100 kW–5 MW range.

Bottom line

Ground mounts and carports: choose HDG steel and save 30–50% per watt. Rooftops and light structures: choose aluminum 6005-T5 with stainless hardware. For coastal extremes, verify the coating specification either way — that is where systems fail early.