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Battery BESS Calculator

Updated

Video presentation

A short video presentation (a webinar) in available here. (Only in Slovene at the moment)

Introduction

The Battery BESS Calculator is a tool designed to calculate the optimal battery that maximizes return of investment for a specific setup.

An electrical battery storage system (BESS) is the key component for optimising energy use and costs. It enables energy arbitrage, allowing electricity to be stored during off-peak hours when prices are low and used or sold during peak times, maximising financial savings. The system also helps control electrical consumption and production, especially when paired with solar energy, by storing excess solar power for later use, reducing reliance on the grid.

Additionally, the battery aids in decreasing costs through peak shifting and load shedding, balancing energy demand and reducing expensive peak-hour consumption. This makes the battery an essential tool for improving energy efficiency, cutting costs, and promoting sustainability.

What is the optimal battery for my setup?

To determine the optimal battery size for your setup, it’s essential to avoid relying on a rough estimate, like simply choosing a battery that is 2 to 4 times the peak power of the solar power plant. While this might be a general guideline, it does not take into account the complexities of your specific system and does not maximize return of investment (ROI).

Instead, a more precise approach requires a detailed analysis of several factors:

  1. Energy price volatility in specific market: The difference and price distribution throughout the day provides opportunity for the earnings through battery arbitrage.

  2. Size of the Solar Power Plant: The total capacity and annual energy production of your plant will help inform the required battery size.

  3. Daily and Seasonal Production Profiles: The PV production patterns of the plant over the course of the day and across the months play a crucial role in determining how much storage is needed to match energy supply and demand effectively.

  4. Self-consumption: The consumption pattern in combination with PV production pattern is the key factor. If consumption peaks during the day (when solar generation is at its highest), the battery size may need to be smaller compared to a setup where consumption is highest during the night or early morning, when solar generation is absent.

To accurately define the optimal battery size, the Reduxi Battery BESS Calculator is a powerful tool. It uses real-world data from your solar power plant, along with consumption information, to provide a tailored and precise battery sizing recommendation. This ensures you’re making an informed investment, rather than relying on rough estimates.

Typical use cases

The battery calculator is a tool designed to estimate the financial benefits—whether savings or earnings—of a battery storage system. It supports several typical use cases:

1. Battery Used Exclusively for Energy Arbitrage

In this scenario, the battery operates solely for energy arbitrage. It charges when day-ahead market prices are low and discharges when prices are high. The benefit—i.e., profit—is directly dependent on the price volatility in the energy market.

2. Battery Covering On-Site Consumption Plus Energy Arbitrage

In this scenario, the battery is installed at a specific site alongside an energy consumer. It stores electricity when prices are low and discharges when prices are high, shifting consumption to more cost-effective periods. The battery is optimized to maximize on-site (self) consumption.
Data required for calculator: Known monthly consumption or, preferably, actual consumption data in 15-minute intervals (e.g. from the grid meter export).

3. Battery Combined with a Solar Power Plant

In this setup, the battery is paired with a solar PV system. Since solar energy is typically generated when market prices are low, the battery allows shifting that energy to more favorable (high-price) hours. The battery must be dimensioned to store and release solar production based on intraday price variations.
Data required: Known installed power of the solar PV system or, ideally, actual 15-minute production data for one full year.

4. Battery + Solar Power Plant + On-Site Consumption

This is the most complex but widely used use case. The solar plant generates electricity during the day, part of which is consumed directly on-site. The battery optimizes energy flows to and from the grid to maximize overall savings or earnings.
Data required: Installed solar power capacity and monthly consumption data. Or — ideally — actual 15-minute interval data for both solar production and on-site consumption over one year.

Application login and licensing information

  • The battery calculator is available at the following link: https://analysis.ai.reduxi.energy/
  • Only licensed users have access to the calculator. Please log in with a Google account to which your license is linked. In case you don't have a valid license, reach out to sales@reduxi.eu to get one.
  • Note: it is also possible to create a Google account using a company (non-Google) email. See here for details. 

Battery calculator usage

After you have successfully logged in it's time to run the battery calculator. In this document we will demonstrate two scenarios: a simple "Battery Used Exclusively for Arbitrage" and a more complex one "Battery + Solar Power Plant + On-Site Consumption". 

The left side menu shows the progress of the calculator. Use "Restart" when a new calculation is to be performed

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Simple scenario: Battery Used Exclusively for Arbitrage

In this example we're going to demonstrate the calculation of earnings when a battery is used only for battery/energy arbitrage. So, the only relevant parameters in the calculation are the battery parameters, energy price and grid information.

1. price and grid parameters

  • the calculator uses the spot (day ahead) market energy price
  • first select the country to define the market of the day ahead price
  • next define the additional fees for purchasing and selling the energy. Usually this is a combination of the energy supplier fee plus the network fee (usually the network free is zero when exporting energy)
  • the import and export limits are defined by the grid operator

2.&3. Electricity meter and solar data upload

When calculating a battery for energy arbitrage only, the electricity meter and solar data are irrelevant. Therefore, they do not need to be provided. So just continue by clicking "No"

4. Analysis

  • At the analysis page, start by selecting the analysis period. We recommend analysing at least one full year to capture seasonal variations—such as winter and summer patterns—and to account for the full range of energy price fluctuations.
  • Then choose a battery of your choice. Define the capacity and c factor. Cycle efficiency, min SoC and max SoC can also be defined. 
  • Click Optimize

Results

The results page shows the key information of the calculation. A battery of 100 kWh brings 3337 EUR income yearly just from the energy arbitrage.

 

5. Report

  • The report page provides detailed information of the battery calculation.
  • It offers printing option
  • At the top the user can add additional information

  • Key data and results

  • The report also gives insights into battery control (for example charging at low prices and discharging at high prices)

  • To calculate the return of investment ROI simply compare the benefits with the investment. 
  • Experiment with different battery sizes and c-rates that gives optimal result for your setup. 

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Complex scenario: Battery + Solar Power Plant + On-Site Consumption

The second example is more complex. It covers an installation with a battery, solar power plant, on-site consumption and battery arbitrage. One can define all relevant parameters or skip some of them when they're irrelevant (e.g. when PV does not exist).

Please have the electricity meter data and solar production data available before continuing. 

1. price and grid parameters

  • The same as in the simple example, define the country and grid parameters

2. Electricity meter

In the second step, please provide the energy consumption and production readings from the electricity meter for the specific location. The electricity meter data is needed to define the on-site consumption. Here you have three options:

a. skip the step in case the on-site consumption is insignificant and not relevant for the calculation

b. If you don't have the data from your electricity meter, but you know approximate profile of your consumption and approximate monthly consumption, please select this

c. however, the most accurate calculation comes from the real electricity meter data. Please provide the data in a csv (comma separated) file in the correct format. Drag and drop the file or load it in the application. The file must contain the following columns:

    • timestamp - ideally in the 15-minute interval (1-hour interval is acceptable. Day intervals are not acceptable, since they lead to inaccurate calculations)
    • consumption (import) of energy or power (in W, kW, MW, Wh, kWh, MWh)
    • production (export) of energy or power can be provided in a separate column or integrated in the 2nd column with a negative sign
  • an example of the meter data is available

  • if the provided data is clear the calculator automatically detects the columns and units. If not, the user is asked to do so. An example of successful detection of the data type is:

  • It's important to specify if the local time is used for the time data or UTC time. If this is incorrectly set, the calculation might be incorrect for a few hours, or can even fail in case the daylight saving time change is incorrect.
  • If the electricity meter data also includes solar production data, mark this as well in the second check mark
  • The calculator also supports the meter data coming from MojElektro (Slovenian portal for grid data measurement). Please see the instructions provided here. 

3. solar data upload

The 3rd step defines the solar production. Also here we have three options:

a. skip this step in case a solar power plant is not and will not be installed on the site

b. select the installed power, if the solar energy production measurements are not available. The calculator defines approximate profile of solar production for a middle European installation.

c. Ideally, the solar power plant data is available. In this case, please provide the production data for the same period and sample time as the electricity meter data. That means the solar production data should also be provided in 15-minute interval. In the same way as in the electricity meter data, please take care about the format of the file (a sample is available). 

4. Analysis

  • Similarly as in the simple scenario, at the analysis page, please define the period and battery information. Again, please test with at least one full year to capture seasonal variations—such as winter and summer patterns—and to account for the full range of energy price fluctuations.
  • Then choose a battery of your choice. Define the capacity and c factor. Cycle efficiency, min SoC and max SoC can also be defined. 
  • Click Optimize

The results of the analysis are more complex compared to the simple scenario and require more explanation

 

1. Consumption cost: Cost of electrical energy consumed by all on-site loads. The cost of electrical energy as provided in the electricity meter data file.
This represents the cost of electrical energy consumed by all loads on the site, assuming all energy would be sourced from the grid. This does not include any battery, any PV production. Solely consumption data. 

2. Battery only income: Revenue generated by the battery through arbitrage only.
This represents the revenue generated by using the battery solely for arbitrage, without any additional loads or production in the system. This is the same as in the simple scenario defined above. 

3. Solar only income: Revenue that would be generated by the solar power plant through selling electricity to the market only. 
This represents the revenue generated by the solar power plant, solely from selling the produced electricity to the market, without any electricity being used for self-consumption. No energy is stored in the battery in this case.

4. Internal consumption savings: Savings achieved using the battery and solar power plant by reducing electrical energy consumption from the grid. The reason for this savings is that there are no supplier and grid costs, when the energy is produced and consumed locally (self consumption),
This represents the savings realized by directly using energy produced by the solar power plant to power all loads in the system (including battery charging), or by utilizing energy stored in the battery to supply all loads in the system.

5. Total: Represents the total cost or earnings of electrical energy.
This reflects the final financial outcome of the system for which the calculation was made, combining all costs, revenues, and savings.

6. Benefits: Represents the total benefits of the battery and solar power plant.
This reflects the final financial benefit of the battery and solar power plant, combining all revenues, and savings.

If one wants to check the total benefit of the battery, but without the solar power plant, then this can be achieved by removing the solar data in the analysis

 

Troubleshooting

  1. In case you see this error

  • Check if you are logged in with the Google account you have the license for.
  • In case, you don't have a license, please reach out to sales@reduxi.eu as explained in the text
  • In case you think this is a mistake, please create a screenshot and send it to support@reduxi.eu

 

2. Cannot proceed by clicking "Next" when uploading measurement data

To continue, you need to define the column names of the timestamp, import and export measurement data as shown below.

3. Data processing error

When uploading the data, an error can be reported when the data is inconsistent. A common case is when the data is uploaded but does not consider the daylight timesaving change correctly.

To continue, please check the uploaded data and correct the values. Double check if the measurement data is stored in the local or UTC time zone. 

4. The application does not work

Click "Restart" and upload the data again. Or try to refresh the page by clicking f5 or as you refresh the page in your browser. 

5. The analysis fails

Check if the input data is correct. Take care about the format of the provided data (for the meter data there has to be a column with time and date and a column with measurement data. And one column needs to have production data. 

 

 

Limitations and future work

  • The current application is based on the day ahead market prices in a specific market. Other pricing models (such as single tariff, base price + dynamic price etc) are not supported.
  • Cost as a result of maximal grid power is not considered in the calculator. The calculator does not considers costs coming from the power peaks. It only considers import and export limits

 

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