Commercial Peak Shaving with Solar + Battery (2026)

What is peak shaving?

Peak shaving means using a battery to discharge during your facility's highest-demand intervals so the utility meter never sees the spike. Your peak demand reading drops; your demand charge drops with it; the battery recharges later when demand is low (and energy is cheap).

For a typical commercial customer with a $20/kW demand charge and a 200 kW peak that hits a few times a month, shaving 50 kW of peak saves about $1,000/month in demand charges alone — before counting any energy savings from the solar generation that's powering the battery. Annualized, that's $12,000+/year just from the demand-shaving function of the system.

Why demand charges exist

Utilities charge commercial customers two prices: an energy charge in $/kWh (how much electricity you use over the month) and a demand charge in $/kW (your single-highest-instant draw during the month). The demand charge pays for the utility's grid capacity to deliver that peak — transformers, conductors, generation reserves — even if you only hit it once for 15 minutes.

For commercial customers, demand charges typically run $10–$30/kW for distribution and another $5–$15/kW for transmission. A 200 kW peak with a combined $25/kW rate costs $5,000/month — even if your average load is 60 kW.

How a battery does peak shaving

So if your peak is 200 kW and you want to shave 50 kW, the threshold is 150 kW. Whenever the building load goes above 150 kW, the battery covers the excess until either (a) load drops below threshold or (b) the battery hits its low-charge limit.

Sizing the battery for peak shaving

Two parameters matter: power rating (kW) and capacity (kWh).

• Power rating must equal or exceed your shave target. To shave 50 kW you need a battery rated for at least 50 kW continuous discharge.
• Capacity must hold enough energy to cover the entire duration of your peak event. A 50 kW shave that lasts 2 hours = 100 kWh of capacity needed.

Dispatch strategy: predictive vs reactive

Modern commercial battery management systems use one of two control approaches:

• Reactive (simple): Battery monitors the meter in real time. When it sees draw above the threshold, it kicks in. Pros: simple, no forecasting required. Cons: can miss the peak if the spike is brief and the battery is slow to react. Also can't optimize for daily-peak prediction.
• Predictive (modern): Battery's BMS forecasts the day's load using historical patterns + weather + scheduling data. It identifies the likely peak window and reserves capacity for that window. Pros: more accurate peak capture, less battery cycling. Cons: forecast accuracy directly drives savings — bad predictions miss the peak (no savings) OR cycle unnecessarily (battery wear).

For sites with predictable daily peaks (manufacturing shifts, office HVAC), predictive control is meaningfully better. For irregular loads (retail with weather-driven spikes), reactive control is more reliable.

Watch out for ratchet clauses

Some utility tariffs have a demand ratchet: this month's billed demand is the higher of (a) this month's actual peak or (b) some percentage (usually 75–90%) of your highest peak in the past 12 months. So a single bad peak month can cost you for an entire year afterward.

If you're on a ratchet tariff, peak shaving is especially valuable: a single prevented peak can save you for 12 months. Conversely, a single missed peak (e.g., during a battery maintenance event) extends your billing exposure for 12 months. Most peak-shaving systems are designed to coordinate with ratchet logic — ask your installer to confirm they're modeling the ratchet correctly.

Combining peak shaving with solar self-consumption

For most commercial sites, the most economical 2026 design uses one battery for two purposes: (1) clip demand-charge spikes AND (2) shift midday solar production to evening peak self-consumption. Modern dispatch logic handles both jobs:

• During the day, the battery charges from solar (free energy).
• If a demand spike occurs, the battery discharges immediately to clip it (priority 1 — demand charges are the most expensive thing on the bill).
• Otherwise, the battery holds capacity for the evening peak, when grid energy rates are highest, and discharges then.

The two functions don't conflict often — demand spikes are typically rare events (a few per month), while solar shifting happens daily. The dispatch logic just prioritizes peak shaving when it sees a demand event coming.

ROI math for peak shaving

Three components of value:

1. Demand charge reduction = avoided kW × demand rate × 12 months
2. Energy charge reduction from solar self-consumption (if combined)
3. Resilience value from backup capability (harder to quantify)

For a typical small-to-mid commercial site (200 kW peak):

The combination of demand-charge reduction + energy savings + tax credits is what gets commercial peak-shaving payback into the 3–5 year range — faster than residential solar by a wide margin. See commercial case study for a fuller worked example.

What to ask before signing a commercial peak-shaving proposal

• Does the proposal model your specific demand profile? Generic 100 kW shaving estimates aren't enough — the installer should pull your last 12 months of interval data from your utility and model actual peak events.
• What's the dispatch logic? Predictive vs reactive; how does the BMS coordinate with solar self-consumption?
• How does it handle ratchet tariffs? If you're on a ratchet, the proposal must explicitly account for it.
• What happens during battery maintenance or failure? Most systems run 1–2 weeks/year offline for service. Confirm the proposal models this loss.
• Demand-charge guarantee? Some installers offer a guarantee on minimum demand-charge reduction. If they don't, ask why.
• FEOC compliance: Modules, inverters, and battery cells must pass the §48E FEOC test for the credit to flow through. See FEOC rules guide.

Frequently asked questions