How to Reduce Peak Demand Charges
with Solar + Battery Storage

The most critical step in demand charge reduction is understanding whenyour peaks occur. You need 15-minute interval data from your utility — this shows your exact power draw at every 15-minute interval throughout the day, week, and year. Most MA utilities provide this data through their online portals (Eversource: "My Account" > "Green Button" data; National Grid: "My Energy Use" > "Download My Data").

When analyzing your load profile, look for these key patterns: (1) Timing of peaks — Do peaks occur in the morning, midday, or late afternoon? Summer or winter? (2) Peak duration — Is the peak a short spike or a sustained plateau? (3) Coincidence with solar production — Do peaks align with solar generation hours (10 AM - 4 PM)? (4) Controllable loads — Are there loads that can be shifted or curtailed during peaks (HVAC, EV charging, process equipment)?

For most Massachusetts commercial buildings, summer peaks occur between 1 PM and 6 PM, driven by air conditioning loads. Winter peaks may occur in the morning (7-9 AM) when heating systems and lighting start simultaneously. Office buildings tend to have a pronounced afternoon peak, while manufacturing facilities may have flatter profiles with peaks during production shifts. Retail locations often peak during evening hours when solar production is minimal.

NuWatt provides complimentary load profile analysis as part of our commercial solar assessment. We import your interval data into our modeling software and overlay it with solar production curves and battery dispatch simulations to identify the optimal demand reduction strategy for your specific building. Request yours through our commercial energy audit and solar sizing guide.

Solar alone cannot guarantee demand charge reduction because production varies with weather and season. Battery storage fills the gaps — providing reliable, dispatchable power exactly when you need it. A properly sized battery system can guarantee consistent demand shaving regardless of solar production, cloud cover, or time of year.

Battery sizing for peak shaving requires two calculations: power capacity (kW) and energy capacity (kWh). Power capacity determines how much demand you can offset at any moment. Energy capacity determines how long you can sustain that output. For demand management, you typically need 2-4 hours of storage at your target discharge rate.

Example sizing: If your goal is to shave 50 kW off peak demand for up to 4 hours (covering the typical 2 PM - 6 PM summer peak window), you need a minimum 50 kW / 200 kWh battery system. We recommend adding 20% buffer: 60 kW / 240 kWh. This accounts for battery degradation, round-trip efficiency losses (typically 5-8%), and the occasional extended peak period.

The battery charges during off-peak hours (overnight or during midday when solar production exceeds building load) and discharges during peak periods. Modern battery management systems coordinate with solar inverters to create a seamless demand-limiting system. When building demand approaches your set threshold, the battery automatically dispatches to prevent the peak from being recorded. Learn more about battery options in our commercial battery storage and ConnectedSolutions guide.