Guide · Solar
Solar Battery Storage Explained
Direct answer
What home battery storage actually does, how the payback maths works, and when adding a battery to existing solar makes sense in Queensland.
Home battery storage is increasingly common on the Gold Coast, but the financial case is more nuanced than the sales material suggests. Whether a battery is the right next investment depends on your tariff structure, your daily consumption pattern, and whether grid resilience matters to you. This guide covers the maths and the design choices.
What a battery actually does
A solar-only system without storage works one direction: solar produces, the house consumes what it can immediately, and the rest exports to the grid for a feed-in tariff (FIT). After dark or on cloudy days, the house imports from the grid at the retail tariff.
Adding a battery changes this:
- Excess solar production charges the battery instead of (or in addition to) exporting
- After dark or on cloudy days, the house consumes from the battery before importing from the grid
- During grid outages, the battery powers critical loads (if the inverter supports it)
The financial benefit comes from the difference between what you pay for grid electricity (typically 30–40c/kWh on Energex retail) and what you get for export (typically 5–8c/kWh feed-in tariff in 2026). Storing your own solar to use later is worth roughly 25–35c/kWh of saved electricity cost.
When a battery makes financial sense
Three things need to align:
1. Your solar already produces more than you consume during the day
If your daily solar production averages less than your daily consumption, a battery doesn’t add much. There’s no surplus to store. You’d be charging the battery from the grid at retail rates and discharging it at the same rates, which only saves the FIT-vs-retail differential.
A typical Gold Coast house with 6.6 kW of north-facing solar produces 25–35 kWh/day on average. A typical 4-bedroom house consumes 18–25 kWh/day. The difference (5–15 kWh/day) is what could go into a battery instead of the grid.
2. The battery is sized to your overnight load
Common mistake: oversizing. A 13.5 kWh battery in a house that uses 5 kWh overnight is excess capacity sitting idle. A right-sized battery covers overnight usage plus a margin for cloudy days.
For a typical Gold Coast house with 18–25 kWh/day total consumption and 5–8 kWh/day overnight:
- 5 kWh battery: covers most overnight loads, $5,000–$7,000 hardware
- 10 kWh battery: covers overnight plus partial cloudy day, $9,000–$13,000 hardware
- 13.5 kWh battery: covers overnight plus partial cloudy day plus some day backup, $12,000–$17,000 hardware
- 20+ kWh battery: full daily-use buffer plus multi-day grid resilience, $18,000–$30,000+ hardware
3. Your tariff structure rewards self-consumption
Time-of-use tariffs (different prices at different times of day) and demand tariffs (penalties for peak usage) make battery storage substantially more valuable. A flat-rate tariff makes it less valuable.
In 2026 Energex retail customers can choose between:
- Flat rate: ~32c/kWh anytime
- Time-of-use: ~22c off-peak (10pm–6am), ~32c shoulder, ~50c+ peak (4–9pm)
- Demand tariff: lower rate per kWh but a charge per kW of peak demand
Battery storage on a time-of-use tariff is dramatically more valuable than on flat rate, because you can shift consumption from peak to off-peak by charging the battery from solar during the day and discharging during peak.
The payback maths
A typical Gold Coast scenario in 2026:
- 6.6 kW solar producing 30 kWh/day average
- House consuming 22 kWh/day, of which 7 kWh overnight
- 13 kWh exported daily without battery
- 8 kWh shifted to overnight use with a 10 kWh battery
Annual savings:
- 8 kWh/day × 365 days × ($0.32 retail − $0.07 FIT) = $730/year
Battery cost (installed): $11,000
Simple payback: 11,000 / 730 = 15 years
This payback period is longer than most batteries’ warranty period (10 years). The financial case alone is borderline.
It improves on time-of-use tariffs:
- 8 kWh/day shifted from peak to overnight use: $0.50 saved minus $0.07 FIT = $0.43/kWh × 8 × 365 = $1,256/year
- Payback: 11,000 / 1,256 = 8.7 years
It improves further if you have an EV charging at home (substantially more daily consumption to shift) or run heavy electrical loads during peak periods.
When battery storage makes sense beyond pure financial payback
The financial case is rarely the whole story. Battery storage delivers value beyond the straight payback calculation:
Grid resilience
The Gold Coast loses grid power 2–8 times per year on average, ranging from a few seconds to several hours. A battery system with backup capability keeps the house running through these events. For homes with refrigerators full of food, medical equipment, work-from-home dependencies, or occupants who depend on consistent power, this is a real benefit.
Note: not all battery installations include backup capability. A “grid-tied battery” without backup is cheaper but only saves money. It doesn’t help during outages. A “hybrid” or “off-grid capable” install with backup is more useful but more expensive.
Future-proofing for time-of-use changes
Energex (and most Australian utilities) are gradually shifting customers to time-of-use tariffs. Within 5–10 years, time-of-use will likely be the default and flat-rate optional. Installing a battery now positions you to benefit from that shift without further capital expenditure.
EV charging optimisation
If you have or are considering an EV, battery storage makes EV charging substantially cheaper. Charge the battery during the day from solar, then discharge into the EV at night. Net cost of EV charging drops to near-zero on a properly sized system.
Off-grid optionality
If you ever want to disconnect from the grid entirely, you’ll need substantial battery storage anyway. Installing it incrementally (battery now, more capacity later) is cheaper than waiting and doing it all at once.
Battery technology choices in 2026
The Australian residential battery market has consolidated around a few dominant chemistries and a few major brands.
LiFePO4 (lithium iron phosphate)
The dominant chemistry for residential storage. Safer than NMC, longer cycle life, slightly lower energy density. Used by Pylontech, BYD, Sungrow, Sonnen, and Victron-compatible third-party batteries.
NMC (nickel manganese cobalt)
Higher energy density but lower cycle life and higher thermal runaway risk. Used historically by Tesla Powerwall (now transitioning to LFP), LG Chem (recalled in 2020), and some Korean manufacturers.
For new residential installs in 2026, LiFePO4 is essentially the only sensible choice unless there’s a specific reason otherwise (Tesla ecosystem buyer, very limited install space).
Major brand comparison
| Brand | Capacity per unit | Indicative installed price |
|---|---|---|
| Pylontech US3000 | 3.5 kWh | $2,800–$3,500 per unit |
| BYD HVM/HVS | 8–22 kWh modular | $11,000–$25,000 |
| Tesla Powerwall 3 | 13.5 kWh | $14,000–$17,000 |
| Sungrow SBR | 9.6–25.6 kWh modular | $11,000–$25,000 |
| Sonnen Hybrid 9 | 9 kWh | $13,000–$16,000 |
Prices include install. Hardware-only is roughly 30–40% lower.
What an integrated install adds
Battery storage on its own is a power system. With Iron and Air’s integration approach, the battery is part of a coordinated system:
- Real-time visibility through Home Assistant: battery state of charge, power flow, current loads
- Smart load shifting: non-essential loads (pool pump, hot water heat pump, EV charging) automatically scheduled when solar excess is available
- Predictive optimisation: weather forecast integration, so the battery’s pre-charge strategy adapts to expected next-day conditions
- Alerts and monitoring: automatic notifications if the battery underperforms, faults, or shows signs of degradation
- Vessel integration (where applicable): same monitoring layer covers shore-side battery and vessel battery for owners with both
This is the difference between a battery that sits there saving money silently and a battery that’s part of an actively managed energy system.
Common questions
Should I add a battery to my existing solar, or is it cheaper to wait? For most homeowners on a flat-rate tariff, the financial case is borderline at current prices. If you’re on time-of-use, have an EV, or value grid resilience, the case is stronger. Battery prices are declining roughly 5–8% per year, so waiting saves money. But tariff changes may make today’s install valuable retroactively.
What about an EV as a battery (V2H/V2G)? Vehicle-to-home (V2H) and vehicle-to-grid (V2G) capabilities are emerging in Australia in 2026 but limited. A few specific EV models support it (some Hyundai, some Kia, some BYD) and a few inverters support it (Sigenergy, recent Sungrow). For most owners, a dedicated home battery is still the better answer in 2026, with V2H as an option to add later.
My retailer is offering a “virtual power plant” (VPP) deal. Should I take it? Worth running the numbers. VPP arrangements typically reduce your battery cost in exchange for the retailer using your battery for grid services. The trade-offs are loss of full control, possible reduced cycle life, and dependence on the retailer’s policies. The financial benefit varies, sometimes substantial, sometimes minor. Read the contract carefully before signing.
What’s the warranty actually worth? Most battery warranties are 10 years or 6,000–10,000 cycles, whichever comes first. This is genuinely meaningful. A lithium battery isn’t going to suddenly fail. The risk is the manufacturer disappearing during the warranty period (less likely with major brands) or the warranty terms being more restrictive than they appear (read the fine print on cycle counting and “normal use”).