Source: Modo Energy, AEMO, supplier disclosures. Merged cells share the same answer.
| AC-coupled | Standard DC-coupled | Reverse DC-coupled | |
|---|---|---|---|
| Configuration | Solar and battery each on their own inverter, merging after conversion to AC to share the grid connection. | One shared (solar/hybrid) inverter. The battery joins after a DC-DC converter and charges directly from the DC output. | One shared (battery) inverter. The solar joins after a DC-DC converter and charges directly from the DC output. |
| Connection points | One shared connection point. | ||
| Land use, layout and fire setbacks | Battery in one compound near the substation, and the solar array sits separate. One set of fire-separation distances for each area. | Battery containers are distributed throughout the solar array beside inverter stations to prevent low-voltage line losses (which are high on DC side). Fire separation repeats at every container. Generally greater land use. | |
| Equipment | Two sets of inverters (battery and solar), two transformers, two MV systems. | One inverter (solar/hybrid), a DC-DC converter, one MV system, one transformer. | One inverter (battery, grid-forming), a DC-DC converter, one MV system, one transformer. |
| Capital costs | Carries the cost of duplicated electrical equipment (higher). | Avoids the cost of duplicated electrical equipment (lower), but carries the cost of the DC-DC converter. | |
| Clipping | Solar generation above inverter capacity is clipped. | Solar can export to the grid and charge the battery at the same time, up to the inverter and battery-charge limits respectively. The value of the excess solar captured may be minimal, given the low price of solar when generation is in excess. | |
| Retrofit compatibility | High. The battery adds on the AC side without touching the solar inverters or array. | Low. The PV array is unlikely to support a distributed battery layout, and older inverter models are unlikely to meet battery requirements, requiring expensive replacement. | Low. The PV array is unlikely to support a distributed battery layout; the inverters would need replacing and the solar rewired to DC-DC converters. |
| Round-trip efficiency for solar charging the battery | Two AC conversions on the battery's solar-charging path. | 1 to 2% efficiency gain over AC; one DC-DC conversion replaces the two AC conversions. | 1 to 2% efficiency gain over AC; one DC-DC conversion replaces the two AC conversions. However, solar exported directly to the grid must pass the DC-DC converter and battery inverter, less efficient than the solar inverter alone. |
| AEMO registration | Two registrations: a semi-scheduled solar unit plus a scheduled BDU, dispatched independently. Two DUIDs. | Default is one DUID (a scheduled bidirectional unit). However, AEMO can approve separate classification as two DUIDs where the operator shows the solar and battery dispatch independently. | |
| Grid forming capability | Qualifies, with a grid-forming battery inverter. Can provide system strength and fast FCAS. | Solar inverter is grid following. Pays system strength charges and misses out on FCAS. New hybrid inverters are beginning to offer grid-forming capability, yet to be proven in practice. | Qualifies, with a grid-forming battery inverter. Can provide system strength and fast FCAS. |
| Battery charging from grid | Yes. | Not with a solar inverter. Possible with a hybrid inverter, but with losses from the inverter and DC-DC converter. | Yes, via the bidirectional battery inverter. |
| Availability | Loss of one inverter does not affect the other asset. | Loss of the inverter blocks both assets. | |
| Delivery risk | Assets can be developed and delivered fairly independently of each other's timelines (approvals, financing, etc.). | Delivery risk of one asset affects the other. | |
| Contracting | Assets can be contracted separately. | Assets need separate grid registration to keep separate SPVs, and careful dispatch management to contract them independently. | |
| Maturity / track record | Proven via retrofits. Quorn Park is the first greenfield AC-coupled system, online in 2026. | First assets come online in 2027. Fulham, Blind Creek and Goulburn solar and BESS are all DC-coupled systems that have received grid connection approval (a 5.3.4A letter). | Smoky Creek and Guthrie's Gap will be the NEM's first utility-scale reverse DC-coupled solar and BESS. Grid connection approval and financing were achieved in May 2026, demonstrating viability of the configuration. |