Why Peak Shaving is the Hidden Saving on Your Commercial Electricity Bill

Most commercial facility managers focus on the energy price — the Arbeitspreis, quoted in ct/kWh — when evaluating electricity costs. That's the number on marketing materials and comparison portals. But for facilities on Mittelspannung (medium voltage) or high-consumption Niederspannung tariffs with annual consumption above approximately 100,000 kWh, the Leistungspreis — the demand charge — is frequently the larger cost driver. And unlike the energy price, the demand charge is almost entirely within your control once you have a battery.

This post explains exactly how the Leistungspreis works, why one 15-minute event per month sets the rate for all 730 hours that follow, and what a correctly sized and controlled battery actually saves for a typical commercial installation.

What Is the Leistungspreis?

The Leistungspreis is the demand charge component of the German commercial electricity tariff. It is assessed per kilowatt (kW) of peak demand registered at the Zählerpunkt (metering point) during the billing period — almost universally one calendar month. The rate is set by the Netzbetreiber (distribution system operator) and varies by region and grid connection level, typically ranging from €8–€18/kW per month for Niederspannungsnetz connections and €6–€14/kW per month for Mittelspannungsanschlüsse.

The metering resolution in Germany for commercial connections above the Registrierung threshold is 15 minutes — one Lastgang interval every quarter-hour, 96 intervals per day. Your monthly peak demand is the highest average power recorded across any single 15-minute interval that month. That single interval determines your Leistungspreis for the entire billing month.

To be precise: the meter records average power in kW for each 15-minute window. If your facility draws 350 kW for 12 minutes and 200 kW for the remaining 3 minutes of a Lastgang interval, the recorded value is approximately 330 kW — the time-weighted average. It is that averaged peak, not an instantaneous spike, that the network operator charges against.

The German Commercial Electricity Bill Structure

A typical German commercial electricity invoice has several components. Understanding which parts are affected by demand peaks and which are not is essential for evaluating the economics of peak shaving.

The Leistungspreis share of 20–40% is the range we see across the commercial facilities we work with in Bavaria and Baden-Württemberg. Facilities with peaky load profiles — cold storage, commercial kitchens, production lines with synchronous motor starts — sit at the upper end. Facilities with flat load profiles (continuous processes) sit lower, but still typically above 20%.

One Peak Sets the Rate for the Entire Month

The economic asymmetry of the Leistungspreis is stark and underappreciated. Consider a logistics facility drawing an average of 180 kW during normal operations, but with a weekly goods-in event on Tuesday mornings where automated dock equipment and refrigeration systems simultaneously start up, momentarily pulling 340 kW for one 15-minute interval.

Without any intervention:

• Monthly peak demand: 340 kW
• Leistungspreis at €12/kW/month: €4,080/month
• Annual demand charges: €48,960

If a battery discharges 100 kW during that Tuesday morning event, capping the grid draw at 240 kW:

• Monthly peak demand: 240 kW
• Leistungspreis at €12/kW/month: €2,880/month
• Annual demand charges: €34,560

Saving: €14,400/year from a 100 kW peak reduction. That saving occurs every month as long as the battery successfully intercepts the demand peak. The battery didn't reduce energy consumption — total kWh consumed is identical. It only changed when the energy was drawn, shifting 100 kW for 15 minutes from a grid peak to a battery discharge.

This is why peak shaving has some of the strongest business cases among battery storage applications: the saving is deterministic (it occurs every billing period), it does not depend on market prices, and it scales with the facility's existing cost structure rather than requiring new revenue streams.

How a Battery Shaves Peaks

Peak shaving requires accurate real-time load monitoring at the grid connection point and fast battery response. The control logic is conceptually straightforward:

1. Monitor current grid draw at the Zähler continuously (typically 1-second polling from a smart meter or TCP/IP power analyzer).
2. Calculate the rolling 15-minute average power — the value that will be reported to the Netzbetreiber.
3. When the projected 15-minute average is on track to exceed the target peak threshold, dispatch battery discharge at a rate sufficient to keep the total grid draw below the threshold.
4. When load drops below the threshold, stop discharge (and optionally begin recharging if prices permit).

The tricky part is step 3. You are working with a rolling average, not an instantaneous value. If you wait until the 15-minute average has already exceeded your target before dispatching the battery, it's too late — the interval is already recording a peak. You need to project forward within the interval and react early.

A simple but effective approach is the "remaining headroom" calculation:

remaining_headroom_kW = (peak_target_kW * 15 - energy_consumed_in_interval_kWh * 4) / remaining_minutes_in_interval

if remaining_headroom_kW < 0:
    discharge_kW = abs(remaining_headroom_kW) + safety_margin_kW

This tells you: given what's already been consumed in this interval, what average power is available for the remaining minutes before the peak is exceeded? If that number goes negative, dispatch immediately. The safety_margin_kW term adds buffer for response latency — typically 5–10 kW for a system with sub-second control response.

Sizing the Battery for Peak Shaving

The sizing question is: how much power (kW) do you need the battery to provide, and for how long (kWh)?

Power sizing is determined by your peak reduction target. If your current peak is 340 kW and you want to hold it to 240 kW, you need 100 kW of battery discharge power. Simple.

Energy sizing is less obvious. For peak shaving, duration matters less than you might think. The longest single demand peak event is bounded by one Lastgang interval: 15 minutes. At 100 kW discharge for 15 minutes, the battery needs only 25 kWh of usable capacity to handle one event. But peaks often cluster — multiple events in a day, or events that span consecutive 15-minute intervals. A practical sizing rule: provide 2× the energy needed for a single event, giving you capacity to handle back-to-back peaks without recharging between them.

For the logistics facility example: 100 kW peak shaving target × 30 minutes effective duration = 50 kWh usable capacity. A 60–75 kWh battery (accounting for depth-of-discharge limits and aging margin) is the right sizing. Going larger adds diminishing returns for peak shaving alone — though a larger battery (100–200 kWh) opens up FCR and spot trading revenue alongside peak shaving, which changes the economics considerably.

We're not saying peak shaving alone justifies a 200 kWh battery investment — at €12/kW/month Leistungspreis, the incremental saving from oversizing the peak shaving battery is marginal. The oversized battery makes sense when you're also using the extra capacity for market trading, and that combined analysis is where the real business case builds.

Combined Returns: Peak Shaving Plus Market Revenue

The encosa architecture treats peak shaving as a hard constraint and market trading as the optimization objective within that constraint. The optimizer commits to protecting the monthly demand peak first — this is non-negotiable because the financial penalty for missing it (an unexpectedly high demand charge for the month) is immediate and certain. Market trading decisions are made in the headroom that remains after peak shaving reserve is maintained.

Concretely: the system maintains a "peak shaving reserve" in SOC at all times during business hours — typically 15–25 kWh set aside and not used for spot market trading. Outside business hours (when demand peaks are not at risk), the full battery capacity is available for EPEX intraday trading.

For a 100 kWh LFP battery at a facility with a typical Bavarian commercial tariff (Leistungspreis €13/kW, annual consumption 600 MWh, current monthly peak 280 kW):

At a battery installation cost of €90,000–€110,000 for a 100 kWh LFP system, this produces a payback period of 5–7 years before battery replacement. The peak shaving component alone — €9,360/year — is what makes that payback achievable. Without peak shaving, the market trading returns alone (€5,700–€8,500/year in this scenario) produce a 10–13 year payback, which is marginal given 10-year battery warranty horizons.

This is the core insight: for most commercial facilities in Germany with metered demand charges, peak shaving is not a "bonus" feature of a battery system. It is the primary economic anchor that makes the investment viable, with market trading as the accelerator on top.