Battery Peak-Shaving Demand-Charge Savings

The demand charge (often $10-30/kW on the single highest 15-minute reading of the month) times the shave, but the shave is energy-limited - a battery holds a given kW reduction only as long as its usable energy lasts (sustainable = usable / duration, actual = min(target, sustainable)). Shaving a 40 kW peak that persists three hours needs 120 kWh; a wide afternoon plateau demands far more storage per kW than a brief spike. The duration comes from an interval-meter load profile. A demand-savings estimate, not a metered bill.

usable_kwh = nameplate_kwh x dod; sustainable_kw = usable_kwh / event_duration_h; actual_shave_kw = min(target_shave_kw, sustainable_kw); annual_savings = actual_shave_kw x demand_per_kw_mo x 12; energy_limited = sustainable_kw < target_shave_kw.

The standard demand-charge peak-shaving method (sustainable shave = usable / duration, actual shave = min(target, sustainable), savings = actual shave x $/kW-month x 12), by name; the relations are public.

The peak-shaving sizing and demand-savings arithmetic are public; utility demand-charge tariffs are published.

Estimate. AHJ and licensed professional govern.

Field names used by the API: nameplate_kwh, dod, event_duration_h, target_shave_kw, demand_per_kw_mo, usable_kwh, sustainable_kw, actual_shave_kw, annual_savings, energy_limited

• Sustainable shave the most a battery can hold for the whole window = usable energy / event durationfirst principles
• Actual shave the lesser of the target reduction and the sustainable reduction (energy-limited when the peak outlasts the energy)first principles
• Savings the actual shave billed at the $/kW-month demand charge over twelve monthsutility demand billing