Home Battery Simulation Website

Hi all

I was bored on Holidays and decided to do some coding (well Gemini 2.5 Pro did..) and try publish my first website…I managed to do my first "Hello World" website easy enough and anyway one thing led to another and I ended up developing a website where you can upload your historical HDF data file and simulate what a house battery would have saved you over the past year, if you don't have one. I'm quite happy with the result and I think it could be quite useful for people.

https://homebatterycalc.netlify.app/

Obviously this started out with a firm focus on my situation, where I have PV but no battery and I wanted to see if I had a 10, 20, 30 kWh battery how much would it save me. I totally Vibe coded this using Gemini AI over the last week, couple of hours here and there and I AM NOT A PROGRAMMER so please be gentle…

Basically you upload your HDF file and it will analyze the last 12 months data, half hour by half hour and simulate a "what if" you had a battery. It runs two scenarios

1. Self consumption - this is simple strategy where it tries to use as much of the solar you generate and not export anything. It will not charge the battery from the grid. People with HDFs that dont have export wont be able to run this scenario..This is crap scenario anyway but maybe if you have a big enough battery and array it might work…
2. Export Maximiser - This is the Meta as the moment here in Ireland..To work this you set up a force charge time (the check boxes in the Tariff entry section) where it will charge the battery and after this time the battery will only discharge, it wont charge off solar. The aim is then only use this if the house is importing. It will then 2 hours out before the next charging time force discharge the battery to empty it as much as possible and getting additional FIT. You enter your MIC and MEC and how much you can charge your battery (inverter power) and it will work to these limits. I wanted to know this since I charge my car and HP so I might not have the spare capacity.

I think its fairly if not very accurate! and the numbers its putting out are what I expected doing excel calcs myself. Have a go and let me know what you think. What is good is that you can game out multiple sizes of battery very easy just change the batt storage and press the run simulation button.

I was able to game out NC7 systems where you have bigger MICs and MECs and bigger chargers. The beauty is it uses your actual data for the last year and for example I was able quickly run through what the savings are between a possible NC7 I'm thinking about. What I found is that Im being limited by the 6kW export with the NC6 to discharge enough to empty the battery if its too big. With the NC7 the sweet spot is 25-30kWh battery even with the NC7

You can review every single day over the past year, just select the month and cycle through the days.

Red line is the simulation line and the dashed line is your actual consumption from last year.

So you can see where the battery made the difference. There might be a slight 30 min shift, but I've been assured by Mr. Gemini its because the HDF data is consumption over the past 30mins and the graphing calculates the power to the end of the half hour period. Getting this graph to work and look good nearly took the longest time, went from bar graphs to area graphs etc so it is what it is….😎

As the readme says I am thinking of adding to this to simulate a PV system but that a whole new ball game where I have to possibly do API call to PVGIS.. so don't hold your breath.

A browser-based tool designed to help Irish homeowners with solar PV systems estimate the potential financial savings of installing a home battery. By uploading their official ESB Networks HDF (Harmonised Data File), users can run a detailed, year-long simulation to see how a battery would have performed with their actual energy consumption and generation data.

Features

• Detailed HDF Parsing: Directly processes the CSV file provided by ESB Networks, ensuring the simulation is based on real-world data.
• Customisable System Configuration: Allows users to set key technical parameters for their battery system, including:
  • Total and Usable Capacity (kWh)
  • Charge/Discharge Rate (kW)
  • Round-trip Efficiency (%)
  • Maximum Grid Import & Export (MIC/MEC)
  • Minimum/Maximum State of Charge (SoC)
• Advanced Simulation Strategies:
  • Self-Consumption: A standard strategy that prioritises storing excess solar power to be used later in the home.
  • Export Maximiser (Tariff Optimiser): An advanced strategy that force-charges the battery from the grid during designated cheap-rate hours.
• Flexible Tariff Options: Supports flat-rate and hourly import/export tariffs to accurately model various energy plans.
• Comprehensive Financial Analysis: Provides clear annual summaries of:
  • Estimated Bill (Before & After Battery)
  • Total Annual Savings
  • System Payback Period
  • Self-Sufficiency Percentage
• Interactive Data Visualisation:
  • Annual and monthly summary cards.
  • Interactive daily charts showing energy flow and battery state of charge.

How to Use

1. Download Your HDF File: Log in to your ESB Networks account and download your detailed Harmonised Data File (HDF) for the last 12-18 months.
2. Open the Website https://homebatterycalc.netlify.app/
3. Upload Your File: In Section 1, click "Choose file" and select the HDF file you downloaded.
4. Configure Your System:
   • In Section 2, enter the technical details of the battery system you are considering. Use the info icons for help on specific terms.
   • In Section 3, choose the simulation strategy you want to model.
   • In Section 4, enter the total installed cost of the system and configure your electricity import/export tariffs. If using the "Export Maximiser" strategy, be sure to select your cheap-rate hours for force-charging.
5. Run the Simulation: Click the "Run Simulation" button at the top of the configuration panel.
6. Analyse the Results: Review the summary cards and interactive charts on the right-hand side to see your potential savings and energy usage patterns.

Technical Details

• The application is a single, self-contained index.html file with no external dependencies beyond the CDN-hosted libraries.
• Frontend: Built with plain HTML, JavaScript, and styled with Tailwind CSS.
• Charting: Uses Chart.js for all data visualisation.
• Icons: Icons are provided by the Lucide icon library.
• Client-Side Simulation: All file parsing and simulation logic runs directly in the user's browser. No data is uploaded to any server, ensuring user privacy.

“Possible” Future Development

• PV Simulation: The next major planned feature is to add a PV (solar panel) simulation mode. This will allow users who do not yet have solar panels to estimate their potential savings by entering their location, system size, and orientation, using the PVGIS API to generate synthetic solar data.

Disclaimer

This tool is intended for estimation purposes only. The financial calculations are based on the data you provide and the simulation logic. Actual savings may vary due to changes in weather, energy usage, and electricity tariffs.