By Dave Miller · off-grid sparky · 22 years wiring solar, batteries and sheds in central QLD

“After my first flat plate boiled dry and burst a pipe in a 45°C central QLD summer, I switched to evacuated tubes and finally got reliable hot water off-grid.”

Look, if you're off-grid in Australia and not using solar hot water, you're wasting money. And if you're choosing between evacuated tubes and flat plates, here's the straight deal.

Evacuated Tubes vs Flat Plate: The Efficiency Truth

Both work. But in Australia's climate? Evacuated tubes win hard.

• Evacuated tubes: Work in freezing temps, dust, and cloudy days. The vacuum inside stops heat loss. You get hot water even on a 5°C morning in Tasmania.
• Flat plates: Only work when it's hot. On a cool spring day? You're waiting for water to warm up. In the outback? They suck in dust and lose efficiency fast.

Practical Tips (No Fluff)

• Size right: 100L tank per person. 3 people = 300L. Oversize or you'll be cold in the shower.
• Insulate pipes: If you don't, you lose 50% of the heat. Use foam pipe wrap. $20. Done.
• Angle the panels: Tilt to your latitude. 35° for most of Australia. South-facing if you're in the north. Simple.
• Drain back system: Mandatory for off-grid. Prevents freezing. Don't skimp.

Australian Suppliers & Pricing (indicative prices)

Don't buy cheap Chinese junk. Get Australian-made or certified.

• Solaris: Evacuated tube kits from $2,200 (2m²). Reliable, 5-year warranty. ($2,200-$2,800)
• Sunnybrook: Flat plate kits from $1,500. Only buy if you're in the tropics and don't care about winter. ($1,500-$1,900)
• EcoSolar: Full off-grid systems (tubes + tank + controller) from $3,800. Includes installation advice. ($3,800-$4,500)

The Bottom Line

Evacuated tubes are $300-$500 more upfront. But they last 15+ years, work in all weather, and save you $1,000+ in backup heating. Flat plates? They're a gamble. In Australia, you don't gamble with hot water.

Get tubes. Install them right. Stop wasting money. Your shower will thank you.

When to Call a Professional

While many off-grid projects are achievable as DIY, certain situations require licensed professionals:

• Electrical work beyond basic 12V DC additions — requires a licensed electrician
• Structural modifications to buildings or load-bearing elements
• Gas line installation or modification
• Solar array installations above safe voltage thresholds
• Any work that affects the structural integrity of your property

Always check local regulations and obtain necessary permits before commencing work.