Key takeaways
- Start with the objective, not the battery size.
- Model when solar surplus occurs and when stored energy has value.
- Backup power and solar self-consumption impose different sizing priorities.
- Compare the full installed and operating system, not a battery-only price.
When battery storage has a clear job
A battery has a clear role when the project can identify energy that is available to store, a later load or constraint it should serve, and a control strategy that connects the two.
- Capture otherwise curtailed or exported solar energy for later site use
- Support defined critical loads during outages
- Limit grid import or manage a measured demand profile
- Coordinate off-grid solar, battery, generator, and load shedding
Data needed before making the decision
Use interval rather than monthly totals whenever possible. The decision depends on the timing of generation and load, the size and duration of peaks, the value or constraint at each period, and the system's recharge opportunity.
- Interval load and photovoltaic production
- Tariffs, export compensation, import or export limits
- Outage frequency, duration, and critical-load list
- Inverter, service, panel, and installation constraints
Check whole-system compatibility
The battery must work with the inverter, communications, operating voltage, charge and discharge limits, protection, transfer arrangement, metering, and control mode. Compatibility should be confirmed for exact models.
- Approved battery and inverter combination
- Normal, outage, islanded, and recovery behavior
- Nominal and usable energy, power, surge, and recharge time
- Installation location, structural support, clearances, and environment
Compare proposals with the same assumptions
Ask every supplier to state the same load, solar, operating window, reserve, losses, and service scope. Without common assumptions, capacity and price comparisons are misleading.
- Modeled energy flows and backup load list
- Usable energy and power at the proposed conditions
- Included equipment, installation, commissioning, monitoring, and exclusions
- Current model evidence, written warranty, and service responsibilities
