Storage with STS vs. storage without STS

What this is about

STS stands for Static Transfer Switch — a fast transfer device that switches defined loads over to the storage system during a grid outage. Whether a system has an STS decides whether it merely shifts energy or can also supply power when the grid is gone.

Storage with integrated STS

Systems like the OmniCube A215 or the Elecnova E10FT container transfer defined backup circuits in under 20 ms — fast enough that controls, IT and many drives ride through with minimal interruption. Planning still matters: grid disconnection, protection systems, inrush currents and bridging time must be engineered per project. An STS does not turn the storage system into a UPS — particularly sensitive individual loads still need their own protection.

Storage without STS

Without an STS, the system operates grid-parallel: it optimizes self-consumption, shaves load peaks and follows its EMS strategy — when the grid fails, it shuts down. For many applications that is entirely sufficient and saves system cost.

Comparison criteria

Criterion	with integrated STS	without STS
Behaviour during outage	defined circuits keep running	shutdown
Transfer time	under 20 ms (A215)	—
Planning effort	backup power concept required	lower
UPS substitute	no — verify per project	no
System cost	higher	lower

The Speichercampus verdict

For pure self-consumption, a storage system without an STS can be sufficient. For backup power, an integrated STS with clear transfer logic is a strong advantage — properly engineered, never promised across the board.

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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