What Is Load Shifting in Battery Energy Storage?

COMMERCIAL BESS ENERGY MANAGEMENT GUIDE

Electricity does not always have the same value throughout the day. A business may have low electricity prices overnight, abundant solar energy at noon and much higher electricity costs in the evening.

Battery load shifting uses energy storage to move electricity from one time period to another. The battery charges when energy is cheaper or more available, then discharges when that stored energy is more useful.

How Does Battery Load Shifting Work?

The principle is easier to understand by looking at a normal operating day.

The important point is that the battery does not create additional energy. It changes when energy is available for use.

Why Do Businesses Use Load Shifting?

The business case usually comes from a mismatch between when energy is available and when it is most valuable.

Load Shifting vs Peak Shaving: What Is the Difference?

These two terms are often used together, but they solve different problems.

For example, a facility may use load shifting to move 300kWh of energy from midday to the evening. The same site could also use the battery for peak shaving when a short production spike pushes grid demand above a target.

For a detailed explanation of the second strategy, read how battery peak shaving works .

Example 1: Time-of-Use Load Shifting

Example 2: Shifting Solar Energy Into the Evening

Load shifting does not have to mean charging from the grid.

Consider a factory with rooftop solar. At noon, the PV array produces 250kW while the facility is using only 180kW.

Approximately 70kW of solar power may be available for battery charging, subject to the charging limits of the BESS.

Later in the evening, the factory still operates but solar production has fallen close to zero. The battery can then return part of the stored daytime energy to the site.

How Much Battery Capacity Is Needed for Load Shifting?

For an early estimate, start with the amount of power you want to shift and how long you need to shift it.

Then allow for:

• Usable depth of discharge
• PCS and system efficiency
• Minimum SOC reserve
• Battery degradation over time
• Expected variation in site load

A battery selected only by nominal kWh can therefore be misleading.

Why Charging Power Matters Too

A battery may have enough kWh for the evening discharge period but still be poorly matched if it cannot recharge within the available charging window.

Suppose 240kWh needs to be restored during a four-hour low-cost period.

The PCS, battery and charging source must be able to support the required charging rate.

If the charging window is only two hours, the required average charging power would be much higher.

When Does Time-of-Use Storage Make Sense?

Load shifting is not automatically profitable simply because electricity prices change during the day.

The price difference needs to be large enough to cover the cost of charging losses and battery cycling.

A useful project review should consider:

• Off-peak electricity price
• Peak electricity price
• Number of shifting cycles per year
• Round-trip efficiency
• Usable battery capacity
• Battery degradation
• System investment
• Operating and maintenance costs

The correct question is therefore not only “What is the peak electricity price?” but also “How much energy can realistically be moved into that period?”

What Role Does the EMS Play?

The battery does not decide by itself when electricity is expensive or when surplus solar is available.

An Energy Management System or other system controller can use information such as:

• Time-of-use tariff periods
• Battery SOC
• Site load
• Solar generation
• Grid conditions
• Backup reserve requirements

Based on the operating strategy, the system can schedule when the battery should charge, wait or discharge.

Can Load Shifting and Backup Use the Same Battery?

Yes, but the system has to balance two competing priorities.

If the battery is discharged deeply every evening to reduce electricity costs, there may be less stored energy available if a grid outage happens immediately afterward.

A project that values backup reliability may therefore keep a minimum SOC reserve.

Can One BESS Do Load Shifting and Peak Shaving?

Yes. In many commercial projects, these functions can be combined.

For example, a battery might:

• Charge from surplus solar around midday
• Hold enough SOC for the expected afternoon peak
• Discharge briefly to reduce the peak
• Use remaining stored energy during a higher-price evening tariff period

The challenge is scheduling the battery so one application does not leave insufficient energy for another.

This is where the control strategy becomes as important as the battery capacity itself.

When Is Load Shifting a Poor Fit?

Not every site needs a time-shifting BESS.

The project may be less attractive when:

• Electricity prices change very little throughout the day
• There is little surplus solar energy
• The high-price window is very long
• The battery would need to cycle heavily for a very small price difference
• The facility's load already occurs mainly during low-cost periods
• The available charging window is too short

In those cases, another BESS application such as peak shaving or backup may provide more value.

What Data Should You Prepare Before Sizing a Load-Shifting BESS?

For a useful project assessment, collect:

Commercial BESS for Load Shifting

The right load-shifting system depends on both power and energy.

The PCS must provide enough kW for the target load, while the battery must provide enough usable kWh for the full shifting period.

You can browse the Voltertech Commercial Energy Storage System range for different C&I battery storage configurations.

For a real project, however, the best starting point is the site's hourly load and tariff data rather than selecting a BESS from catalogue capacity alone.

Frequently Asked Questions

Load Shifting Is About Timing, Not Just Battery Capacity

The value of BESS load shifting comes from using stored energy at a more useful time.

That might mean moving low-cost grid electricity into an expensive tariff period, moving midday solar into the evening, or combining both strategies.

The best projects start with three things: the load profile, the tariff schedule and the available charging window.

Once those are clear, the required battery kWh, PCS kW and operating strategy can be defined much more accurately.