Solar for metal fabrication and engineering workshops in Australia: one shift, sharp peaks (2026)

In short

• A workshop that runs one weekday shift uses about two thirds of its solar. The rest goes to the grid at the weekend for a small credit.
• In our example a 30kW system pays back in about 2.2 to 3.0 years, and a 100kW system in about 2.5 years.
• Welders, compressors and the 7am start set the demand charge. Solar does not touch that. Size the system to the shift, not the roof.

Solar pays on most Australian engineering and metal fabrication workshops, but the return is set by the weekday shift, not the size of the roof. A workshop that runs 7am to 4pm, Monday to Friday, uses most of what a right-sized system makes while the shift is on and exports the rest on Saturday and Sunday. This page goes deeper than our manufacturing guide on the two things that decide a workshop's result: the self-use share on a single shift, and the demand charge that welders and compressors set.

Why is a workshop's load different?

A fabrication shop draws power in spikes. A MIG or TIG welder pulls a heavy load for seconds at a time. A plasma cutter, a press brake, a CNC mill and a compressor each add their own short peaks. Between them the average load is modest, but the busiest half-hour, usually when everything starts at once in the morning, is high. That busiest half-hour is what a demand charge bills you for.

Then the shop closes. From 4pm to 7am and all weekend, the load drops to lighting, security and a compressor leak-down. Solar makes nothing after 5pm, and on a weekend it has nowhere to go.

So two numbers matter more for a workshop than for most sites: the share of solar used on site, which is lower than a factory running two shifts, and the demand charge, which solar rarely lowers.

What's a realistic payback for a workshop?

Here is a worked example with made-up figures. These are example figures, not our prices or a real site. Both rows use Brisbane output of about 1,450 kWh per kW a year, $0.28 saved for each kWh used on site, and $0.05 for each kWh exported.

The 30kW sums: 32,625 kWh × $0.28 = $9,135, plus 10,875 kWh × $0.05 = $544. Yearly saving $9,679. The price range is the one on the cost page, so the payback is a range too.

The smaller system uses a higher share of its output because the shop's weekday load covers it with room to spare. Go bigger and the extra panels make power at the same hours as the first ones, when the shop is already covered, so more of it is exported. That is why a workshop is often better served by 30kW to 50kW than by filling the roof. A larger roof does suit a shop with a paint booth, a furnace or a second shift. See is 30kW big enough and 50kW: how your opening hours change the payback.

Will solar lower our demand charge?

Usually not, and a quote that claims it should show its working. A demand charge is set by the single busiest half-hour in the billing period, often at 7am when the compressor, the extraction fans, the lights and the first welders start together. The sun is low then. Solar can lower a peak that falls at 1pm on a hot day; it cannot lower one at 7am.

Three things do lower a workshop's peak:

• A staggered start. Compressor first, then extraction, then welders ten minutes later. No cost.
• A soft starter or variable speed drive on the compressor. Removes the biggest inrush.
• A battery sized for the peak, not for overnight. It discharges for the half-hour that matters. Test it against the demand charge in dollars, which is on your bill. See demand charges explained and commercial solar batteries.

Ask for the demand charge saving on its own line in any proposal. If the line says zero, that is an honest quote.

What does the STC discount look like at this size?

Small-scale technology certificates are created upfront on the system size, your zone rating and the years left in the scheme. For a system installed in 2026 the scheme counts five years. A 30kW system in Brisbane (zone 3, rating 1.382) earns 30 × 1.382 × 5 = 207 certificates, rounded down. At whatever price the installer is trading them, that is the discount line on the quote. The number of certificates is easy to check yourself against the Clean Energy Regulator's calculator; the price per certificate moves with the market. See how STCs work for business.

What about tax for a small workshop?

From 1 July 2026 a small business with turnover under $10 million can write off eligible assets costing under $20,000 each in full. A 30kW system costs more than that in our example, so it goes into the small business pool instead, depreciated at 15% in the first year and 30% each year after. Larger businesses use the general rules. Ask your accountant; the answer depends on your structure.

Does the state add anything for a workshop?

The federal STC discount applies everywhere. Victoria is the one state with a commercial solar incentive: Victorian Energy Upgrades gives an upfront discount on systems between 30kW and 200kW through an accredited provider, so a Victorian workshop sizing at 30kW sits right at the threshold and should ask the installer whether the system qualifies. The full state table is on the manufacturing guide.

What should a workshop send for a proposal?

Just one recent electricity bill, every page. Using the meter number on it, our team gets your interval data, which shows the shift hours, the weekend load and the half-hour that sets your demand charge. There is nothing to request from your retailer.

Already have a quote? Compare it line by line with our checklist. Otherwise send the bill.

What should a workshop ask an installer?

• What self-use share does the saving assume, and is it from our interval data or a default?
• Is the demand charge saving on its own line, and is it zero?
• Why this size and not smaller? What does the last 10kW earn?
• Is the switchboard rated for the inverter, or is an upgrade priced in?
• Does the roof need structural work, and is it a quoted figure or "subject to inspection"?