AC-coupled vs. DC-coupled

What this is about

The coupling type describes where PV system and storage are electrically connected: on the alternating-current side (AC) behind the PV inverter, or on the direct-current side (DC) before conversion. Both work — with different consequences for efficiency, retrofittability and control.

AC coupling

With an AC-coupled system, the existing PV installation stays untouched: the PV inverter keeps feeding the site’s grid, and the storage system charges and discharges via its own inverter (PCS). That makes AC coupling the first choice for retrofits. The drawback: on its way into the battery, PV power passes through two additional conversions (DC→AC→DC), which costs efficiency.

DC coupling

In a DC-coupled system, PV strings connect directly to the storage system’s MPPT input — up to 50 kW on the OmniCube A215. PV power charges the battery without the detour through the AC side, and under feed-in limitation the system can absorb energy that would otherwise be curtailed. In return, DC coupling needs more planning and suits new PV strings and targeted expansions best.

Comparison criteria

Criterion	AC coupling	DC coupling
Existing PV systems	ideal, no intervention	rarely sensible
New build / PV expansion	possible	the concept’s strength
Conversion losses PV→battery	two extra conversions	minimal
Using feed-in limitation	limited	curtailed energy can be stored
Planning effort	lower	higher (string design)

The Speichercampus verdict

AC is often strong with existing systems. DC is interesting for new builds, PV expansion and an integrated MPPT. With the A215, the two worlds are cleanly distinguished: existing PV stays on the AC side, new strings use the MPPT.

Next step

Send us your load profile, electricity bill, PV data and project goal. Speichercampus assesses which storage capacity, power and product class make sense.

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