Stationary storage is on-site energy storage that is fixed in place (not a vehicle battery) and used to store electricity for later use. In EV charging projects, stationary storage most commonly refers to battery energy storage systems (BESS), but it can also include other technologies such as thermal storage or flywheels in broader energy applications.
For EV charging infrastructure, stationary storage is primarily used to manage site power constraints, reduce costs, and improve charging availability.
Why Stationary Storage Matters in EV Charging
EV charging demand can be spiky—especially at commercial car parks, depots, and charging hubs. Stationary storage helps sites:
– Reduce peak demand and avoid demand charge penalties
– Stay within a maximum site demand limit when multiple chargers run at once
– Add more chargers sooner by deferring grid reinforcement
– Shift energy use to off-peak periods for better tariff outcomes
– Increase self-consumption of on-site solar PV by storing excess generation
This can make the difference between a small pilot site and a scalable rollout without immediate grid upgrades.
How Stationary Storage Works at a Charging Site
A typical stationary storage setup is controlled by an energy management system (EMS):
– Storage charges when site load is low or electricity is cheaper
– Storage discharges when EV charging demand rises
– The EMS coordinates storage with load management across chargers
– Power is managed to protect the grid connection and optimize cost
In some designs, storage supports only EV chargers; in others it supports the whole building load.
Common Use Cases
Stationary storage is widely used for:
– Fleet depots with high simultaneous charging demand
– Workplace charging where grid capacity is limited
– Public charging hubs targeting high utilization
– Sites with long grid upgrade lead times
– Solar PV sites aiming for more renewable charging
Key Benefits
– Lower operating costs through peak shaving and tariff optimization
– More usable capacity from an existing grid connection
– Improved scalability for phased charger rollout
– Better renewable utilization when paired with PV
– Potential resilience benefits, depending on system design and controls
Limitations and Design Considerations
– Additional CAPEX and space requirements
– Safety, thermal management, and permitting considerations
– Round-trip energy losses reduce overall efficiency
– Control strategy must be tuned to real load profiles
– Storage sizing depends on charging patterns, dwell times, and peak duration
Stationary Storage vs Managed Charging
Stationary storage is often used together with smart controls:
– Managed charging shifts when vehicles charge
– Load balancing shares power across chargers
– Stationary storage supplies extra power when demand peaks
Combining these approaches can maximize throughput while keeping the site within connection limits.
Related Glossary Terms
Stationary Battery Storage
Battery Energy Storage System (BESS)
Load Management
Load Balancing
Peak Shaving
Peak Demand
Maximum Site Demand Limit
On-site Solar PV
Grid Capacity Assessment