Peak Shaving Baseline SOC and Reserve SOC Explained

In battery energy storage systems (such as hybrid inverters, or EMS-controlled batteries), Peak Shaving Baseline SOC and Reserve SOC both define a minimum battery charge level, but they serve different purposes.

1. Reserve SOC

Reserve SOC is the battery capacity that is kept available at all times and is normally not allowed to be discharged during regular operation.

Purpose

• Provides backup energy during grid outages.
• Protects battery life by preventing deep discharges.
• Ensures a minimum amount of energy is always available.

Example

Battery capacity: 10 kWh
Reserve SOC: 20%

• 20% (2 kWh) is protected.
• The battery can only use the remaining 80% (8 kWh) for self-consumption, TOU, peak shaving, etc.
• Once SOC reaches 20%, discharging stops.

Behavior:

2. Peak Shaving Baseline SOC

Peak Shaving Baseline SOC is specifically used within the peak shaving function.

Purpose

• Ensures enough energy remains in the battery for future peak demand events.
• Prevents the battery from becoming completely depleted before a peak load occurs.
• Defines the minimum SOC that the peak shaving algorithm may discharge to.

Example

Battery capacity: 10 kWh
Peak Shaving Baseline SOC: 40%

When peak shaving is active:

• Battery discharges to reduce grid import peaks.
• Once SOC reaches 40%, peak shaving stops.
• Grid power will then supply any additional load.

Behavior during peak shaving:

How They Work Together

Suppose:

• Reserve SOC = 20%
• Peak Shaving Baseline SOC = 40%

The system will typically behave as follows:

During Peak Shaving

The battery can discharge only down to 40%.

During Self-Consumption

Depending on system settings, the battery may continue discharging below 40%.

During Backup Mode

The battery will never discharge below 20%.

Are They Almost the Same?

Functionally they are similar because both are SOC thresholds.

However, their objectives are different:

So:

• Reserve SOC = hard floor.
• Peak Shaving Baseline SOC = peak-shaving floor.

The battery usually cannot go below Reserve SOC under normal conditions, while Peak Shaving Baseline SOC only controls how much capacity peak shaving is allowed to use.

Practical Example

If a customer sets:

• Reserve SOC = 30%
• Peak Shaving Baseline SOC = 50%

Then:

1. Peak shaving can use battery energy from 100% down to 50%.
2. At 50%, peak shaving stops.
3. Self-consumption (if enabled) may continue discharging from 50% to 30%.
4. At 30%, all regular discharge stops and the battery energy is reserved for backup.

This means Peak Shaving Baseline SOC is generally a more conservative threshold than Reserve SOC, ensuring energy remains available for later peak events while still maintaining the ultimate backup reserve.