Battery Time-Shift Modeling

Battery Time-Shift Modeling is the analytical process used to simulate how energy storage systems shift electricity consumption or solar generation from one time period to another—typically from low-value hours to high-value hours. It allows solar designers, EPCs, developers, and energy analysts to predict how a battery will charge and discharge throughout the day to maximize financial return, reduce peak demand, improve self-consumption, or optimize TOU (Time-of-Use) performance.

This type of modeling is essential in modern solar + storage design because utilities increasingly use dynamic pricing, demand charges, and export limitations. Accurate time-shift modeling ensures batteries are sized correctly, programmed efficiently, and financially justified within the customer’s tariff structure. Many design teams use advanced platforms like Solar Designing and performance tools in the Solar Project Planning Hub to run these simulations.

Key Takeaways

Battery Time-Shift Modeling predicts how a battery charges and discharges to reduce energy costs and increase solar value.
Essential for designing solar + storage systems under TOU rates, demand charges, export limits, and self-consumption goals.
Helps determine optimal battery size, strategy, and financial return.
Works best with accurate load profiles, solar production, and tariff data.
Strongly supported by automated solar design tools such as SurgePV.

What Is Battery Time-Shift Modeling?

Battery Time-Shift Modeling is a simulation that predicts:

When the battery will charge (excess solar, off-peak grid hours)
When the battery will discharge (peak pricing hours, high demand periods)
How much energy will shift from one time window to another
Financial impact on utility bills, demand charges, and ROI

It considers real-world constraints such as inverter limits, battery SOC (State of Charge), round-trip efficiency, load profiles, solar production patterns, and tariff structures.

This modeling enables designers to answer questions like:

How much solar generation should be stored instead of exported?
Is a battery more valuable for peak shaving or load shifting?
What battery size maximizes customer bill savings?
How should the battery be programmed for TOU periods?

Related concepts include Load Analysis, TOU Rate Modeling, and State of Charge (SoC).

How Battery Time-Shift Modeling Works

Battery time-shift workflows vary by software, but most follow this general process:

1. Import Solar Production & Load Profiles

Designers use irradiance models, consumption data, or monitoring exports.

2. Identify Peak, Part-Peak & Off-Peak Periods

TOU structure defines when electricity is expensive or cheap.

3. Determine Battery Charging Windows

The system prioritizes:

Excess solar generation
Off-peak grid energy
Export-limited periods

4. Determine Battery Discharging Windows

Discharging targets:

Peak rate periods
High-demand intervals
When self-consumption is more valuable than export

5. Apply Battery Constraints

Time-shift modeling factors in:

Round-trip efficiency
Charge/discharge rate limits
Battery capacity
Inverter AC/DC conversion limits
SOC floors and ceilings

6. Calculate Financial Impact

Software models:

Bill savings
Demand charge reductions
Arbitrage revenue
Export-limitation benefits

These simulations help determine optimal battery size and control strategy.

Types / Variants of Battery Time-Shift Modeling

1. Solar Self-Consumption Time Shifting

Battery captures surplus solar for evening use—common in residential markets.

2. TOU Arbitrage Modeling

Charge during low-price hours and discharge during expensive periods.

3. Peak Demand Shaving

Battery discharges during short high-load spikes to reduce demand charges.

4. Export Limitation Mitigation

Used when utilities restrict export (e.g., zero-export sites).

5. Backup Preparedness Modeling

Evaluates keeping a percentage of SOC reserved for outages.

6. Grid Services / VPP Time-Shifting

Aggregated batteries participate in grid support programs.

How It’s Measured

Battery time-shift models typically measure:

Energy Shifted (kWh/day or kWh/month)

Amount of energy moved from one period to another.

Peak Demand Reduction (kW)

How much battery shaved off the monthly peak.

Financial Savings ($/month)

Tariff-based value from shifting energy.

Solar Self-Consumption Rate (%)

Percentage of solar used on-site rather than exported.

Battery Utilization Rate (%)

How actively the battery cycles throughout the billing period.

Round-Trip Losses (kWh)

Energy lost during charge/discharge cycles.

Net System ROI

Often evaluated using tools such as the Solar ROI Calculator.

Typical Values / Ranges

Residential

Daily shift: 3–12 kWh
Battery size: 5–20 kWh
Time-of-use savings: 10–40%

Commercial

Daily shift: 20–300 kWh
Peak shaving: 10–50 kW
Savings often depend on demand charge structure.

Utility-Scale

Daily shift: MWh scale
Applications include arbitrage, peak management & grid services.

Values vary widely based on tariff structures, solar generation, load profiles, and battery configuration.

Practical Guidance for Solar Designers & Installers

1. Always start with accurate load profiles

Garbage inputs = garbage outputs.

2. Map TOU periods and demand charges early

Use utility rate databases or customer bills.

3. Choose control strategies carefully

Common strategies include:

Solar-first
Peak-first
TOU-first
Export-prevention

4. Ensure inverter and battery power ratings align

See Inverter Sizing.

5. Model both energy and power impacts

Shifting kWh and shaving kW both matter financially.

6. Use a realistic SOC range

Most batteries operate between 10–90% SOC for longevity.

7. Validate results using multiple scenarios

Peak days, cloudy days, weekends vs. weekdays.

8. Present results cleanly using proposal tools

Time-shift results integrate well into Solar Proposal Software.

Real-World Examples

1. Residential TOU Optimization

A homeowner with TOU rates shifts 8 kWh/day from midday solar excess to evening peak hours, reducing monthly bills by 30%.

2. Commercial Peak Shaving

A logistics center uses a 100 kWh battery to reduce a 150 kW afternoon peak down to 98 kW, saving thousands per month in demand charges.

3. Export-Limited Site

A commercial building subject to zero-export rules uses time-shift modeling to store midday solar instead of exporting it. Energy is released in the evening to offset grid purchases.