Cutting Commercial Demand Charges with Battery Storage

Commercial grid tariffs charge a demand (capacity) component based on your highest measured 15-minute load in the billing period. A battery storage system performs peak shaving: it covers those short peaks from stored energy, lowering the measured billing demand. Whether it works in practice depends on correct sizing, load forecasting and clear discharge priorities.

How the demand charge is billed

In commercial grid-fee structures, the capacity price (Leistungspreis) is set by the single highest quarter-hour load measured during the billing period. One brief spike can define the demand charge for the entire term, even if average consumption is far lower.

Because a single 15-minute interval drives the cost, reducing that one peak — rather than total energy use — is what lowers the demand component. This is the mechanism peak shaving targets.

How a battery shaves the peak

A battery storage system discharges precisely during the short load peaks, supplying the additional power from stored energy instead of drawing it from the grid. This caps the load seen at the meter and reduces the billing demand (Bemessungsleistung).

The effect only materialises when three conditions hold together: the battery is sized for the peaks that actually occur, the load is forecast well enough to discharge at the right moment, and peak shaving is prioritised over competing uses of the same storage.

Sizing the battery to the load profile

Correct sizing starts with a detailed analysis of the load profile. It reveals the consumption patterns and the magnitude and duration of the peaks the battery must cover, so the storage can be dimensioned to the real demand rather than to assumptions.

Both power (kW) and energy (kWh) matter: the battery must deliver enough power to flatten the peak and hold that output for the full duration of the peak interval. Undersizing on either dimension leaves part of the peak uncovered and weakens the demand-charge reduction.

Forecasting and discharge priority

Peak shaving depends on discharging at the right quarter-hour. This requires a load forecast good enough to anticipate the peak, plus a control logic that keeps enough charge in reserve for it.

When the same battery is also used for other purposes, priorities must be defined so that peak-shaving capacity is not spent beforehand. Without that prioritisation, the storage can be depleted when the peak arrives and the demand reduction is lost.

Combining peak shaving with dynamic tariffs

The same battery can also respond to dynamic electricity tariffs, where the purchase price follows the exchange and changes every quarter hour. Here the storage charges during cheap (sometimes negative-price) periods and discharges when prices are high.

A power price manager can coordinate the battery for these applications. Because peak shaving and price-based charging draw on the same storage, the control logic must reconcile them — reserving capacity for the demand peak while still using idle capacity to exploit price spreads, where the spread justifies the cost per cycle.