Peak Shaving Battery Storage Sizing Guide

Convert the load curve into a duty cycle

Choose a candidate grid setpoint and calculate the load above that setpoint for every interval. The highest difference indicates the required discharge power. The accumulated energy above the line indicates the discharge energy needed during each event. Repeat the calculation across the year rather than sizing from one monthly bill peak.

For a first estimate, required battery energy equals the sum of shaved kW multiplied by interval duration, then adjusted for conversion losses, usable SOC and margin. Final modeling should use the actual dispatch time step and equipment constraints.

Size power and energy separately

A short motor or process peak can require high PCS power but little energy. A long afternoon plateau can require modest power and much more energy. Treating both projects as the same kWh system produces weak results.

Check PCS continuous rating, overload duration and reactive-power obligations. If the PCS must also support voltage, power factor or backup transfer, those functions may reduce the power available for peak shaving.

Test charging and reserve constraints

A battery that shaves the morning peak may not have time to recharge before the afternoon peak. Model charger or PCS limits, import headroom, PV surplus, site operating schedule and minimum SOC. Where backup is required, reserve energy must remain protected unless the operating policy explicitly allows its use.

Forecast error matters near the setpoint. Add an EMS control band so the system does not chatter between charge and discharge, and include measurement latency and ramp limits in performance testing.

Measure the result after commissioning

Acceptance should confirm meter location, setpoint logic, sampling interval, response time, SOC limits and data export. After commissioning, compare baseline peaks, controlled grid demand, battery power and SOC. This evidence is required to tune the strategy and verify economic performance.