By Dave Miller· off-grid sparky · 22 years wiring solar, batteries and sheds in central QLD
“After losing 14 hours of power in a 45°C heatwave, I learned that grid-tie inverters are useless for backup unless you manually isolate them from the grid.”
Grid-Tie Battery Inverters: Backup & Sell-Back for Aussie Homes
First up: if you're living off-grid (no power lines), you don't need a grid-tie inverter. You need a battery-based system. But if you're connected to the grid (which you are if you've got a power bill), and want backup during blackouts + to sell excess solar, read this.
First up: if you're living off-grid (no power lines), you don't need a grid-tie inverter. You need a battery-based system. But if you're connected to the grid (which you are if you've got a power bill), and want backup during blackouts + to sell excess solar, read this.
What You Actually Get
Grid-tie with battery isn't "off-grid" – it's grid-connected with backup. Here's the deal:
Backup during blackouts: When the grid dies, your battery powers critical loads (fridge, lights, phone charging). No more spoiled food.
Sell excess solar: When you generate more than you use, you send it to the grid and get paid (feed-in tariff). In most states, that's 6c-10c per kWh.
Warning: Not all "grid-tie" inverters with battery give backup. You need a hybrid inverter (like Enphase, Tesla, or Victron). Don't buy a standard grid-tie inverter and expect backup – it won't work.
Australian Pricing & Suppliers (indicative prices)
Don't expect to pay less than $12k for a proper system (battery + inverter + installation). Here's what's actually available:
Tesla Powerwall: $12,000 - $15,000 (plus installation). Sold by most major installers (e.g., SolarQuotes, SunWiz).
Enphase IQ Battery: $10,000 - $13,000. Check Enphase's approved installer list – they're strict about who can sell it.
Victron Energy: $10,000 - $14,000. Aussie-owned. Get quotes from Victron dealers (e.g., victronenergy.com).
Tip: Size your battery for critical loads only. A 10kWh battery (like Powerwall) runs a fridge, lights, and phone for 4-6 hours. Don't buy a 5kWh if you want to cook dinner during a blackout.
Practical Tips: Don't Get Screwed
These are non-negotiables for Aussie homes:
Feed-in tariff is low: Don't assume you'll get $0.50/kWh. Most states pay 6c-10c. Check your energy provider's current rate.
Backup isn't automatic: Ask your installer: "Will this run my fridge during a blackout?" If they say "yes", get it in writing. Many systems don't.
Don't buy cheap: $8k systems? They're usually a scam. You'll get a battery that dies in 2 years. Stick to the big names.
Check your roof: If you've got a 5kW solar system, you can't add a 10kWh battery without upgrading your inverter. Get a pro to check first.
Bottom line: If you want backup and to sell solar, a grid-tie battery system is the way to go. But don't buy the first thing you see. Get 3 quotes. And for god's sake, don't try to DIY it – it's dangerous and illegal without a license.
⚠️ SAFETY WARNING: Working with electrical systems, structural modifications, or gas installations carries inherent risks. If you are not confident in your abilities, always engage a licensed professional.
In the “How Many Batteries to Power a House?” video, Nick walks through a straightforward sizing method using daily kWh usage and desired days of autonomy – the same calculation I outline in the guide when choosing a grid‑tie battery inverter for reliable backup.— Dave Miller
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.
