AC coupling
AC coupling in the SpeicherCampus context: typical for existing PV systems. Technically, the term is usually described as connection on the alternating-current side.
What does AC coupling mean?
With AC coupling, PV system and storage are connected on the alternating-current side: the PV inverter feeds the site’s grid as usual, and the storage system charges and discharges via its own PCS. Both systems remain electrically independent and meet at the shared AC bus.
That makes AC coupling the standard for retrofits: the existing PV stays untouched, warranty and metering unchanged. The price is an efficiency loss, because PV power is converted twice more on its way into the battery.
What matters in practice
- ideal for existing PV systems with a working inverter
- metering concept: the storage EMS needs a measuring point at the grid connection
- budget conversion losses of roughly 4-8 % in the charging path
- combinable with DC-coupled expansions on the same storage system
Practical example
A business with a five-year-old 99 kWp system adds a 215 kWh storage unit on the AC side. No intervention in the PV, two days of installation — the self-consumption rate rises from 45 to 78 %.
The SpeicherCampus perspective
For existing installations SpeicherCampus almost always recommends AC coupling; for new builds and expansions the DC path via the MPPT is calculated as the alternative.