These two terms are used interchangeably in almost every ESS sales conversation — and it's costing buyers money. They are fundamentally different strategies with different value drivers, different system requirements, and different financial returns.
Peak Shaving
The ESS discharges during the facility's own consumption peaks to reduce demand charges and avoid utility penalty thresholds.
- Value driver: your own demand charge structure
- Target: facility peak demand windows
- Battery cycling: partial, irregular
- Primary savings: demand charge reduction
- Best for: high-demand-charge markets
Arbitrage
The ESS charges during cheap off-peak grid hours and discharges during expensive peak grid hours, capturing the price spread as profit.
- Value driver: grid tariff spread (time-of-use)
- Target: grid price peaks and troughs
- Battery cycling: full, daily, predictable
- Primary savings: energy cost + demand charge
- Best for: markets with wide TOU spreads
Peak Shaving — How It Works
Every industrial facility has a monthly electricity bill that includes two components:
- Energy charge: based on kWh consumed × rate per kWh
- Demand charge: based on peak kW draw during the billing period — typically the highest 15–30 minute average during the month
Demand charges can represent 30–50% of a large industrial facility's total electricity bill. For a facility paying €8,000/month in demand charges, reducing peak demand by 100kW can save €2,000–€4,000/month — entirely independent of energy arbitrage.
Peak shaving works by detecting when the facility's load is approaching its monthly peak — and discharging the battery to suppress that peak. The battery is strategically idle much of the time. Cycling is irregular and partially predictable.
Arbitrage — How It Works
In a time-of-use (TOU) tariff structure — which describes most European C&I markets including Italy, Spain, and parts of the UK — electricity prices vary throughout the day based on supply and demand on the grid.
Arbitrage exploits this variation systematically. The ESS charges when prices are low (typically night hours, 11pm–7am) and discharges when prices are high (morning and evening peaks). The spread between charge and discharge price is captured as economic value — every day, predictably.
This is a fundamentally different activity from peak shaving. Arbitrage is about time-shifting energy purchases. Peak shaving is about suppressing consumption peaks.
Why They're Often Confused
Both strategies use the same equipment — a battery, an inverter, and an EMS. In practice, most well-designed C&I ESS systems pursue both simultaneously:
- The EMS monitors both the facility's load profile AND the grid tariff schedule
- It dispatches the battery to shave the facility's demand peaks AND to capture arbitrage spread
- The result is a blended return from both mechanisms
This is why the confusion persists: in real deployments, the two strategies are usually running in parallel. But for financial modeling purposes, understanding which is the primary value driver matters for sizing and ROI projection.
Which Strategy Dominates at Your Facility?
Which Markets Favor Which Strategy?
Italy: Arbitrage-dominant. Wide TOU spread (~€0.26/kWh) makes arbitrage the primary IRR driver. Demand charges exist but are secondary.
Spain: Arbitrage-dominant. Similar TOU structure to Italy, though spread is slightly narrower. Growing demand charge component.
UK: Mixed. Many UK industrial tariffs are still single-rate energy + demand charge. Peak shaving can be equal or greater value than arbitrage depending on the tariff structure.
Germany: Peak shaving dominant. German industrial tariffs have lower TOU spreads but high demand charges — peak shaving is often the primary mechanism.
Ask your ESS supplier to model both strategies separately in their financial analysis. If they're presenting only one number without explaining which mechanism is driving it, you may be missing half the picture.