TL;DR
- Three-phase unlocks >10 kW systems and keeps voltage rise within network limits.
- Our commercial inverter shortlist: Sungrow SG, Fronius Tauro, GoodWe MT/UT.
- Battery sizing logic is different from residential — demand charges, not Time of Use, drive ROI.
- Typical 100 kWh BESS installed: $130k-$180k before incentives.
Why three-phase matters
Single-phase inverters above 5 kW cause voltage rise on long feeders. QLD network rules typically require three-phase for:
- Solar systems > 10 kW.
- Commercial premises with three-phase loads (motors, compressors, commercial A/C).
- Battery systems > 10 kWh with inverter output above 5 kW per phase.
Commercial inverter shortlist (2026)
| Inverter | Rating | Best for |
|---|---|---|
| Sungrow SG50CX | 50 kW | 50-60 kW rooftop, cost-effective |
| Sungrow SG110CX | 110 kW | 100-150 kW industrial rooftop |
| Fronius Tauro ECO 99-3-P | 99 kW | Where serviceability matters |
| GoodWe MT-G2 (25/50 kW) | 25-50 kW | Small/mid commercial with battery-ready |
| Sungrow SBR + SC50HV | 25-100 kWh | Commercial BESS paired with solar |
When a commercial battery pays off
Residential batteries chase Time-of-Use peak rates. Commercial batteries chase demand charges:
- If your monthly bill shows a demand charge of $8-$25/kW × measured peak kW, a battery that shaves that peak has quick payback.
- Example: cold-storage site with 120 kW measured peak, $18/kW demand charge = $2,160/month. A 100 kWh battery can often shave 30-40 kW peak, saving $540-$720/month on demand alone.
BESS sizing
Three inputs: (1) demand-charge window length (Ergon 30-min interval), (2) typical shoulder-peak kW excursion magnitude, (3) operational cycles per year. Most Mackay commercial BESS land at 50-200 kWh usable, with 30-100 kW inverter output.
UPS vs BESS
A BESS is not a UPS. Transfer times of 10-100 ms during grid outages are fine for most loads (refrigeration, HVAC, office) but critical servers/medical equipment still need a dedicated UPS upstream. We can design hybrid systems that combine both.
FAQs
Can I upgrade from single-phase to three-phase?
Yes. Cost typically $3k-$8k depending on distance from Ergon's network transformer. We coordinate the upgrade application with Ergon as part of the commercial project.
Is there a rebate for commercial batteries?
The Federal Battery Booster scheme primarily targets residential. Commercial incentives come through STC (systems up to 100 kW), depreciation and specific schemes like the Small Business Energy Incentive (check current eligibility).
Commercial battery modelling
We ingest your Ergon interval data and model BESS sizes against demand charges.
Request feasibility