OPENEVSE IS A HOME EV CHARGER THAT CAN RUN ONLY ON YOUR LEFTOVER SOLAR AND NEEDS NO VENDOR ACCOUNT
An open-source car charger that can throttle itself to charge only from the solar you would have exported, and you never need a vendor account.
by OpenEVSE
EnergyHome
- difficulty
- ●●●●○
- time
- a weekend plus installation
- license
- GPL-3.0
- repo
- repo ACTIVE151 stars
●●●●○ · a weekend plus installation · GPL-3.0 · 151 stars · repo ACTIVE
WHAT YOU’LL NEED
- 3D printer + filament — printable parts — files are in the repo
- Electronic parts — full list with part numbers in the repo BOM
- Dev board / microcontroller — runs the project firmware
Partner
COMPAREE VERDICT
OpenEVSE is the only open-source EV charger that has shipped thousands of units and stayed maintained. The firmware handles the J1772 state machine, monitors temperature through an MCP9808 sensor, and enforces current limits with ammeter calibration. The ESP32 gateway is what most people actually want: it reads your solar inverter or home-energy monitor over MQTT or HTTP, then starts, stops and modulates charging to match surplus production. Fifty recurring weekly timer slots, session limits by state-of-charge or energy, load shaping to stay inside your supply rating, and RFID per-user logging are all evaluated on the device, not in a cloud account. The control page lives at openevse.local; Emoncms, MQTT and OCPP integrations are optional. The hard part is not the build — it is the wall side. A dedicated 240-volt circuit is regulated work in most countries, and you will need a permit and an electrician unless you already hold the licence yourself. If that barrier does not apply, or you are willing to pay for it, this is the only charger in the driveway that does not phone home. The one thing most likely to go wrong is assuming eco mode is the default: it is a setting you enable after install, and the firmware will happily charge at full rate if you skip that step.
IN THE REPO
NOT IN THE REPO
- —Safety firmware is GPL-3.0 and implements SAE J1772 Level 1 and Level 2 with ground-fault, stuck-relay and missing-ground detection.
- —Separate ESP32 gateway firmware adds solar divert (eco mode), timers, RFID authorisation and a local web UI.
- —The project sells a 349-dollar DIY kit and a 659-dollar assembled 48-amp station; both include the boards and sensors.
- —The supply-side wiring is a dedicated 240-volt circuit, which in most jurisdictions requires a permit and a licensed electrician.
- —Gerbers, schematics and assembly guides are in the repository; you can also buy the boards pre-populated.
- —Licence permits commercial use.
Can I build this?
This build involves mains voltage — for adults comfortable with electrical work only.
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
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Videos
OpenEVSE build and installed charger
No official project video; the repository contains written assembly guides and the web UI is documented in the wiki.
Gallery
Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the assembly guide in the hardware/ folder and decide whether to buy the kit, the assembled station, or just the Gerbers and self-source.(The v5 board is current; earlier revisions are deprecated.)
- 2.Check your local electrical code for EV charger installation requirements — most jurisdictions require a permit and a licensed electrician for the supply circuit.(The low-voltage assembly is not the hard part; the mains side is.)
- 3.If you plan to use solar divert, confirm your inverter or energy monitor can export data over MQTT or HTTP; the list of tested integrations is in the ESP32 gateway wiki.(Eco mode is not automatic — you configure it after install.)
- 4.Order the kit or assembled station from openevse.com, or download the Gerbers and order bare boards from your preferred fab.(The project sells hardware to fund development; buying from them is the easiest path.)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
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KNOWN ISSUES
- The supply-side wiring is a dedicated 240 V circuit, which in most places means a permit and an electrician. Do not assume you can install this yourself unless you already hold the licence.
- Eco mode (solar divert) is a setting you enable, not the default behaviour. If you skip configuration, the charger will run at full rate.
- The project sells two versions: a 349-dollar kit that requires assembly, and a 659-dollar pre-assembled 48 A station. If you have never soldered a through-hole board, buy the assembled one.
- The enclosure is sold separately. You can buy the official one or use a standard outdoor NEMA box, but the box must be rated for the current and outdoor use if the charger is outside.
- The ESP32 gateway and the safety controller are separate boards with separate firmware. Both must be flashed and working for solar divert to function.
- RFID authorisation requires an RC522 or PN532 reader module, which is not included in the base kit. If you want per-user logging, order that separately.
Can I charge at full rate even if I do not have solar?
Yes. Eco mode is optional. Without it, the charger behaves like any other Level 2 station and charges at the rate you set in the web UI.
What inverters and energy monitors work with solar divert?
Any device that can export real-time power data over MQTT or HTTP. The gateway wiki lists tested integrations, including Fronius, SolarEdge, Enphase, SMA, and generic Modbus or REST endpoints.
Do I need Home Assistant or another hub?
No. The charge rules and timers run on the ESP32 itself. Home Assistant, Emoncms and OCPP are optional integrations for logging or remote control, not requirements.
What is the difference between the 349-dollar kit and the 659-dollar assembled station?
The kit ships as bare boards, components and connectors; you solder and assemble it. The 659-dollar station is pre-assembled and tested, rated for 48 A continuous.
Can I use this in a country that does not use J1772?
The firmware implements J1772, which is the standard in North America. For IEC 62196 Type 2 (Europe, Australia), you would need to adapt the connector and verify the pilot-signal levels match the standard. Some users have done this, but it is not officially supported.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
The 349-dollar kit requires assembly; the 659-dollar station is pre-built and tested. Which would you pick, and does solar divert tip the decision for you?
OpenEVSE
OpenEVSE started in 2011 as a safety-certified open-hardware EV charger, back when the only alternative was a proprietary station tied to a vendor account. The project has shipped thousands of kits and pre-assembled units, and the firmware has been independently tested for SAE J1772 compliance. The ESP32 gateway was added later to support solar divert and local control without requiring a cloud service.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM19d agoedited
Practical notes from our verification: the ESP32 gateway repository has 228 stars and is actively maintained separately from the safety-controller firmware. The project sells hardware directly, which funds ongoing development — buying from them is the simplest path, though you can also order bare boards from the Gerbers. The single biggest trap is assuming eco mode is automatic: it is a setting you configure after install, and the firmware will happily charge at full rate if you skip that step. The mains-side installation is regulated work in most countries; the repository documents the low-voltage assembly, but you will need a licensed electrician and a permit for the supply circuit unless you already hold the licence yourself.