Key takeaways
- Power in kW and energy in kWh solve different parts of the operating problem.
- Monthly bills cannot reveal the timing and duration of site peaks.
- The operating strategy should be simulated before a cabinet or container is selected.
- Balance-of-system, grid, thermal, fire, and service scope belong in the same proposal.
1. Define the operating objective first
A storage system should have a ranked job: peak management, photovoltaic self-use, backup, charging support, grid service, or a defined combination. The priority changes both the required power and duration.
- Write one measurable success condition for each objective.
- Identify conflicting objectives, such as preserving backup reserve while dispatching for tariff savings.
- Define normal, outage, maintenance, and communication-failure modes.
2. Collect the data that exposes the real load
Use timestamped load, tariff, photovoltaic, production, outage, and interconnection data. At minimum, the analysis must show how high the load becomes, how long it stays high, and when surplus energy is available.
- Interval site demand and energy
- Tariff periods, demand rules, and export limits
- Photovoltaic production or curtailment
- Critical loads, motor starts, and production schedules
- Transformer, service, and point-of-connection limits
3. Separate power from energy duration
The kW rating sets how much instantaneous demand the system can serve; usable kWh sets how long it can do so. A long-duration low-power profile can need a very different system from a short high-power peak.
- Size discharge power against the coincident controlled load.
- Size charge power against available grid or renewable surplus and recharge time.
- Calculate duration with usable energy and conversion losses.
- Test performance after applying project reserve and aging assumptions.
4. Compare complete configurations
Compare candidate systems on the same duty and responsibility scope. Nameplate price or capacity alone omits the PCS, EMS, switchgear, transformer, cooling, fire, commissioning, and site work that determine project fit.
- Nominal and usable energy at the proposed operating window
- Continuous and overload power at site conditions
- Thermal architecture and environmental limits
- Controls, metering, communications, and remote support
- Included equipment, services, exclusions, and acceptance criteria
