Powerbeat
Introduction
After analyzing my solar data of 2023 and visiting the Intersolar trade fair in June 2024, I realized I was in need of a new kind of a HEMS (Home Energy Management System). Here’s my view on “How I would design and build a Home Energy Manager for me”.
Sneak preview
Here’s a first screenshot of Powerbeat as sneak preview. Powerbeat is the internal project name of my hypothesis for an UI prototype. More screens are on the next pages.
Learnings & Assumptions
My learnings as solar owner:
- Using too many Apps - Currently, I use the Tesla app to monitor the status of my Powerwall battery system. For solar energy forecasting, I rely on the SMA app. Additionally, I use EVcc to charge my electric vehicle using solar power and to check the dynamic electricity prices from Tibber.
- Summer Mode vs Winter Mode - A typical solar system in Germany is oversized during the summer and undersized during the winter. So the HEMS needs to run in different modes.
- Unpredictable Consumption - At least for me my usage is not unpredictable. Mainly the car usage (because it’s the biggest consumer), but also smaller energy consumers like washing machine and so on.
- Daily Solar Production - It’s all about the daily solar production. Even the monthly and yearly solar production numbers look impressive, important is to charge the home battery for the night and the car on a daily basis. As result I started categorizing each day into <20 kWh, 20+ kWh, 40+ kWh, 60+ kWh and 100+ kWh buckets:
| Daily Production | Day Category | Category Label |
|---|---|---|
| 0-20 kWh | Grid Import needed | Red |
| 20-40 kWh | House only | Orange |
| 40-60 kWh | House plus | Blue |
| 60-100 kWh | Charge car | Green |
| 100+ kWh | Full charge | Yellow |
Increasing Complexity
- Grid only (Year 2000) - One fixed price per kWh all the time. There was no need to optimize the power consumption from a personal level.
- Solar system (Year 2012) - With solar panels on the roof you produce more power during day and nothing during the night. Plan to use more energy, when the sun is shine, and less, when it’s not.
- Home battery (Year 2018) - During the day charge your home battery in order to use the energy during the night. Goal is to use only your own produced energy and not import anything from the grid.
- Dynamic power plan (Year 2022) - With dynamic pricing our provider will offer the hourly prices from the European Energy Exchange. On average the kWh price fluctuates between 18 Euro-Cents and 34 Euro-Cents.
- Battery charging from Grid (Year 2024) - As default your home battery will only be charged by solar power. But for most home batteries charging from the grid can be enabled. And with a dynamic pricing you can charge at low price and use the energy during high price timeframes. An advantage during winter days with snow on the solar panels.
- Battery grid export (Future Year 2025) - The home battery doesn’t just store energy for personal use anymore, it can now export stored electricity back to the grid during peak hours. By selling energy when demand is high, it enhances energy flexibility and supports grid stability.
- Bidirectional car charging (Future Year 2026) - Electric vehicles equipped with bidirectional charging capabilities allow your car’s battery not only to power your vehicle, but it can also supply electricity back to your home or the grid. The car can provide additional energy, reducing reliance on grid electricity and further optimizing energy costs.
User Interface
In my opinion a great Home Energy Manager consists of the following components:
| Powerbeat Now |
Powerbeat Today |
Powerbeat Devices |
Powerbeat Insights |
|---|---|---|---|
| Energy flow in real-time |
Today’s data and forecast |
Charging Planner |
GenAI-powered Reports |
| Status quo of the energy flow at this moment of time. | Show all details about today’s solar production, forecasts and pricing. | Decide how devices and cars will be charged. | Use LLM (Large Language Model) to create reports. |
| Data in kW: Solar power, Battery Charging, Home usage, Grid export and more. |
Data in kWh: Generated today, Forecast rest of the day (best & worst), Comparison to last days and more. |
Charging Modes: Charge on solar, Fast charging, Minimum Charging, Disabled and more. |
Reports: Top 10 days this year so far?, Home usage per month?, Battery charge cycles per week? |
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| Now | Today | Devices | Insights |
Next
As next step please explore the details of the Powerbeat Now screen.