Peak Shaving Savings Calculator
Demand charges — billed on a facility's highest measured demand (kW) over the billing period, not on total energy used — can account for 30-70% of a commercial or industrial electricity bill. Peak shaving attacks that charge directly: reduce demand during the specific window the utility measures for peak billing, and the demand charge falls even if total energy consumption stays the same. This calculator takes your original peak demand, the amount of peak reduction you can deliver, your demand charge rate, and your billing periods per year, then reports the reduced peak demand and the monthly and annual demand charge savings. For a comprehensive demand-charge bill analysis and optimization strategy, see our Demand Charge Optimizer, and for the full ROI of a behind-the-meter battery built around peak shaving, see our Behind-the-Meter BESS ROI Calculator.
Your facility's current peak demand — the highest instantaneous kW draw the utility measures over the billing period, which sets your demand charge.
The amount of peak demand reduced through battery discharge, backup generation, or load shifting during the utility's peak measurement window.
The $/kW demand charge rate from your utility tariff — applied to your measured peak demand each billing period.
How many billing periods your utility uses per year — most are monthly (12), but some commercial tariffs bill on a different cycle.
original peak demand (kW) − peak reduction from shaving (kW)
peak reduction from shaving (kW) × demand charge rate ($/kW)
monthly demand charge savings ($) × billing periods per year
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
How we calculate this →Peak shaving delivers savings through pure demand reduction, not energy reduction -- a facility doesn't need to use less electricity overall, just less at the specific moment the utility measures peak demand. Shaving 200 kW off a 1,000 kW peak saves $3,000 a month at a $15/kW demand charge rate, or $36,000 a year -- the same math whether that reduction comes from a battery discharging during the peak window, a backup generator, or simply shifting flexible loads to off-peak hours.
How peak shaving savings are calculated
This calculator quantifies the demand-charge savings from reducing your facility's peak demand, independent of how that reduction is achieved (battery, generator, or load shifting). Three quantities tie the calculation together.
Reduced Peak Demand (kW) = Original Peak Demand (kW) − Peak Reduction from Shaving (kW). The reduced peak is what the utility will measure after your peak-shaving action engages during the peak window. At the defaults (1,000 kW original, 200 kW reduction), that is 1,000 − 200 = 800 kW.
Monthly Demand Charge Savings ($) = Peak Reduction from Shaving (kW) × Demand Charge Rate ($/kW). Demand charges are billed on the highest measured kW each billing period, so every kilowatt shaved off that peak saves the full demand rate for that month. At 200 kW shaved and $15/kW, that is 200 × $15 = $3,000/month.
Annual Demand Charge Savings ($) = Monthly Demand Charge Savings ($) × Billing Periods per Year. Because the demand charge recurs every billing period (assuming the peak is shaved consistently each period), annual savings scale linearly with the number of periods. At $3,000/month and 12 periods, that is $3,000 × 12 = $36,000/year.
Two notes on the model. First, this is a demand-charge-only calculation — it excludes any energy (kWh) arbitrage revenue a battery might also earn by charging off-peak and discharging on-peak, and any effect on time-of-use energy charges; a battery that shaves peak will often capture those benefits on top. Second, real-world savings depend on actually hitting the peak window every billing period — if the peak occurs at an unexpected time or the shaving resource is unavailable, that month's demand charge is not reduced, so dispatch reliability matters. Data sources: Peak shaving technology and demand charge reduction methodology from NREL and EPRI (Electric Power Research Institute) battery storage and demand management studies; demand charge structure and peak measurement windows from utility rate tariffs and FERC regulations; battery energy storage system performance and dispatch strategies for peak shaving from NREL battery storage research and case studies; backup generator and load-shedding peak shaving strategies from commercial and industrial energy management literature; demand charge savings calculations from utility bill analysis and energy management software documentation. Verification: with defaults (1,000 kW peak, 200 kW reduction, $15/kW, 12 periods), Reduced Peak Demand = 800 kW, Monthly Demand Charge Savings = $3,000, Annual Demand Charge Savings = $36,000.