What you log per charge
- Odometer reading, kWh added, AC or DC session
- Location (quick-chips or free text), and optional cost
- State-of-charge percentages. If your charger only shows %, Joulie does the kWh math for you.
Track EV charging sessions, efficiency, cost, and CO2. One joule at a time.
About
Joulie is a clean, no-nonsense Android app for electric vehicle drivers who want to know exactly how their car uses energy. Log each charge and Joulie tracks the numbers that actually matter.
What Joulie shows you
- Efficiency in km/kWh, kWh/100 km, or mi/kWh across any time period
- Cost per km or per 100 km, with mixed-currency warnings when relevant
- AC vs DC breakdown charts, monthly kWh and cost trends, battery degradation over time
- CO2 emissions versus a petrol-car baseline, fed by opt-in live grid intensity from Electricity Maps with a dashboard pill that tells you at a glance whether now is a good time to charge
Privacy by design
No analytics, no telemetry, no crash reporting. Your charge data stays on your device unless you explicitly enable Drive backup, and even then only this app can read what it wrote.
Features
- Multi-car support with a top-bar switcher and per-car or global resets.
- Home-screen widget showing your last charge at a glance.
- Optional Google Drive backup. Opt-in, stored in your private App Data folder only.
- CSV export via the standard Android share sheet, full-history or date-ranged.
- Material 3 theming with light, dark, and system modes.
- Available in English, Greek, Turkish, and Russian, with an in-app picker plus the OS-level Android 13+ entry.
- Charts: efficiency trend, monthly kWh and cost, AC vs DC split, top locations, battery degradation, CO2 cumulative.
- kWh-from-SoC calculator for chargers that show only state-of-charge percentages.
- Themed icons on Android 13+; the bolt-J adopts your wallpaper accent.
- Live CO2 tracker with opt-in Electricity Maps integration: a dashboard pill shows the current grid carbon intensity for your zone, colour-coded across five bands so you know at a glance whether now is a good time to charge. Each charge event is logged with the grid intensity at save time. On-device 1-hour cache respects the free-tier rate limit.
FAQ
- Does Joulie need an account?
- No. The app runs entirely offline by default.
- Does Joulie collect my data?
- No analytics, no telemetry, no crash reporting. Charge data stays on your device unless you explicitly enable the optional Google Drive backup, and even then only this app's signing certificate can read what it wrote.
- How do I install it?
- Download the latest signed APK from the Releases page and side-load it. A Play Store listing is on the roadmap.
- Where do I report a bug or request a feature?
- Open an issue on the GitHub repo.
- Can I see the source?
- Yes. Joulie is licensed under the GNU General Public License v3.0 or later; the full source is at github.com/SPS-L/joulie.
Privacy
- The app does not collect analytics, telemetry, or crash reports.
- All charge data is stored locally in the app's private database.
- Google Drive backup is opt-in. When enabled, a JSON snapshot is written to your Drive's hidden App Data folder, accessible only to this app's signing certificate.
- The Electricity Maps grid-intensity feed is also opt-in. When enabled, only your zone code and personal API key leave the device; no charge data, location, or personally-identifiable information is sent.
Full policy: Privacy Policy.