Answer
OCPP (Open Charge Point Protocol) is the open protocol a charger uses to talk to a charging management system. For solar charging, an energy manager reads PV surplus and sends the charger a charging profile that sets a current limit. OCPP 1.6 supports basic smart charging, and 2.0.1 adds a device model and ISO 15118 support.
Can an EV charger really follow your solar panels? Yes, and OCPP is a protocol many third-party energy managers use to do it. The energy manager reads PV output and household load, then tells the charger how much current it may draw. The hard parts are the minimum charging current, the OCPP version, and a charger that lets you point it at your own back-end.
Last updated: November 2026.
This guide is for installers, EPCs and technically minded owners who need to specify an OCPP-based solar and EV setup. It sticks to what the Open Charge Alliance and open-source project documentation publish. Where a number is an example, it says so.
- What OCPP is and what the Open Charge Alliance publishes
- How OCPP 1.6, 2.0.1 and 2.1 differ
- How a charging profile steers a charger from PV surplus
- Why the 6 A minimum sets the surplus threshold
- Where ISO 15118 fits
- A charger checklist and a commissioning checklist
Sizing PV for an EV charger?
Model the array and its yield in SurgePV first, so the surplus your charger can use is based on a real roof design.
Book a DemoChecking cost first? See the SurgePV pricing page.
What Is OCPP and Why Does It Matter for Solar?
OCPP is an open protocol that lets EV charging stations talk to charging management systems. The Open Charge Alliance FAQ describes it as an open protocol for communication between charging stations and a central system, developed and maintained by the Open Charge Alliance (OCA) to keep hardware and software interoperable.
The OCA is a non-profit organization founded in 2014 (Open Charge Alliance, About us). Per its FAQ, the OCPP specification is freely available to download. The OCA publishes the specification, a compliance test tool and a certification program, not software libraries.
For solar, OCPP matters for one reason. It is the common way to send a changing current limit to a charger that the energy manager’s maker did not build. An inverter or meter knows the surplus. An energy manager turns that into a limit. OCPP carries the limit to the charger.
Key Takeaway
OCPP does not measure solar. It carries the instruction. The solar logic lives in the energy manager, and the charger only follows the limit it is given.
OCPP 1.6 vs 2.0.1 vs 2.1: What Changed?
Three versions are current. The OCA lists OCPP 1.6 (2015), OCPP 2.0.1 (2020) and OCPP 2.1 (released January 2025). The OCA says plainly that 1.6 and 2.0.1 are not compatible, while 2.1 is backward compatible with 2.0.1.
| Item | OCPP 1.6 | OCPP 2.0.1 | OCPP 2.1 |
|---|---|---|---|
| Released | 2015 | 2020 | January 2025 |
| Smart charging | Load balancing and charge profiles | Added smart charging functions | Improved smart charging |
| ISO 15118 | Not listed by the OCA | Native support for ISO 15118 Plug and Charge | Adds ISO 15118-20 with bidirectional power transfer |
| Device management | Not listed | Get and set configuration, monitoring | Builds on 2.0.1 |
| Other listed features | SOAP and JSON versions, local list management | Improved transactions, added security, display and messaging | DER control, bidirectional charging (V2X), battery swapping |
| Compatibility | Not compatible with 2.0.1 | Not compatible with 1.6 | Backward compatible with 2.0.1 |
Sources: Open Charge Alliance, OCPP page and Open Charge Alliance FAQ, read 4 November 2026. The OCA also says OCPP 2.0.1 edition 3 was approved as an IEC standard, IEC 63584, in 2024, and that the industry is moving toward OCPP 2.x.
The OCA calls OCPP 1.6 widely implemented, so many installed chargers speak it. It gives no market-share figure, so this page does not either.
Pro Tip
Check which OCPP version the energy manager and the charger both speak before you buy either. Because 1.6 and 2.0.1 are not compatible, a manager that only speaks 1.6 cannot drive a charger that only speaks 2.0.1.
How Does a Charging Profile Follow Solar Surplus?
An energy manager sends the charger a charging profile, and the charger limits its current to what the profile allows. In OCPP 1.6 the message is SetChargingProfile. The fields below come from the OCPP 1.6 SetChargingProfile JSON schema in the open-source ocpp Python library.
| Field | Allowed values | Purpose |
|---|---|---|
| chargingProfileId | Integer | Identifies the profile |
| stackLevel | Integer | Priority when several profiles apply |
| chargingProfilePurpose | ChargePointMaxProfile, TxDefaultProfile, TxProfile | Station-wide cap, default for new sessions, or limit for the running session |
| chargingProfileKind | Absolute, Recurring, Relative | How the schedule is anchored in time |
| chargingRateUnit | A or W | Limit in amps or watts |
| chargingSchedulePeriod | List of start offsets and limits | The schedule itself |
The manager repeats a simple loop. It works out surplus as PV output minus household load, converts it to a current limit, and sends an updated profile. The Home Assistant integration documents the same idea: its ocpp.set_charge_rate service takes a limit in amps (integration documentation).
Worked example with made-up numbers. PV output is 5,000 W and the house uses 1,200 W. Surplus is 3,800 W. On a single-phase charger at 230 V, 3,800 / 230 = 16.5 A, so the manager sets a limit of 16 A (3,680 W). Rounding down avoids importing from the grid.
Why Does the 6 A Minimum Set the Solar Threshold?
A charger cannot deliver less than 6 A and keep charging. The evcc documentation on solar charging states that this follows from the minimum current of 6 A specified in the charging standard IEC 61851. Multiply by phases and a nominal 230 V and you get the minimum surplus needed to start.
| Charging setup | Calculation | Minimum surplus to charge |
|---|---|---|
| Single-phase | 1 x 6 A x 230 V | 1.4 kW |
| Three-phase | 3 x 6 A x 230 V | 4.1 kW |
- Single-phase charging1.4 kW
- Three-phase charging4.1 kW
Source: evcc documentation citing IEC 61851 (6 A x 230 V x phases), checked 4 November 2026.
Below the threshold the session pauses or draws from the grid. evcc also says surplus charging does not work on systems with regulated “zero export” grid limits, because no surplus reaches the grid meter. For chargers without phase switching, the evcc FAQ says it can make sense to use a single phase so smaller surplus is usable.
Will your roof clear the 4.1 kW threshold?
Check how often the array output beats house load, using SurgePV roof modeling, shading analysis and energy-yield modeling.
Book a DemoChecking cost first? See the SurgePV pricing page.
Pro Tip
For a small array, ask whether the charger and the car can charge on one phase. The single-phase threshold of 1.4 kW is reached much more often than 4.1 kW, so more of the car’s energy can come from solar.
Where Does ISO 15118 Fit with OCPP?
ISO 15118 and OCPP cover different links. ISO 15118 is the vehicle-to-grid communication standard between the car and the charger. OCPP runs between the charger and the back-end. A Plug and Charge setup needs both.
The OCA says OCPP 2.0.1 includes native support for ISO 15118 Plug and Charge. Plug and Charge means the vehicle identifies itself when plugged in, with no RFID card or app step. OCPP 2.1 adds ISO 15118-20, including bidirectional power transfer for vehicle-to-grid use. See our vehicle-to-grid glossary entry for the basics.
Most home solar-following setups do not need Plug and Charge. They need a current limit that changes as the sun does, and OCPP 1.6 profiles already provide that.
How Do Home Energy Managers Use OCPP?
Many energy managers act as the OCPP central system. The charger is set to connect to the manager’s address instead of the maker’s cloud, and the manager sends the profiles.
The open-source Home Assistant OCPP integration is one public example. Its README says it supports OCPP 1.6j, 2.0.1 and 2.1 (experimental) (Home Assistant OCPP integration on GitHub). Its documentation covers a central-system setup, charge profiles such as TxProfile and an ocpp.set_charge_rate service with a limit in amps. The solar logic itself, the surplus calculation, is yours to build as an automation.
This page does not compare named energy managers or chargers. Each maker’s own documentation is the only reliable source for what its product supports, and we did not use those pages here. Ask each vendor for a written statement of OCPP version, configurable back-end address and any paid feature unlock.
What Should You Check Before Buying a Charger?
Use this checklist. Each item is a question to put to the charger maker in writing.
- Does the charger let you set your own OCPP back-end address, with no cloud account?
- Which OCPP version does it run, and does your energy manager speak the same one?
- Is OCPP enabled out of the box, or behind a paid unlock?
- Is the model on the OCA certified products list? The OCA says its certification covers OCPP 1.6 and 2.0.1 and uses the official compliance test tool.
- Does it support phase switching, and can the car charge on one phase?
- What is its minimum charging current, and what limit range does it accept?
Further Reading
For the load-management side of the same project, see smart EV charging load management with solar.
How Do You Commission an OCPP Solar Charging Setup?
Work through the connection, then the control, then the solar logic. These are practical checks, not manufacturer specifications.
| Symptom | Likely cause | What to check |
|---|---|---|
| Charger never connects | Wrong back-end address or charger ID | Address and ID entered in the charger, and the manager’s port |
| Charger connects but ignores limits | Profile purpose or stack level does not fit | Use TxProfile for the running session and TxDefaultProfile for new ones |
| Charging stops and starts | Surplus swings near the minimum | Add a hold time or minimum-surplus threshold in the manager |
| Car never starts on solar | Surplus is below 1.4 kW or 4.1 kW | Compare real surplus with the thresholds above |
| No surplus ever shows | Zero-export limit on the grid connection | Check export settings with the installer |
Commissioning order:
- Confirm the charger connects and reports status to the manager.
- Send a fixed limit and check that the charger follows it.
- Test a low limit and confirm the charger pauses below the 6 A floor.
- Turn on the solar loop and watch a full sunny day and a cloudy day.
- Record the settings in the handover pack.
What Should You Do Next?
Three actions follow from the protocol picture.
- Pick the version pair first. Match the energy manager’s and charger’s OCPP versions, then choose hardware.
- Do the 6 A math. Compare your array’s real surplus with 1.4 kW and 4.1 kW before you promise “solar-only” charging.
- Get the back-end address in writing. Do not accept “OCPP compatible” as an answer.
Ready to size the PV side? Book a SurgePV demo, or look at the generation and financial tool and shading analysis. For design background, read the solar and EV charging integration guide and home EV charging with solar optimization.
Frequently Asked Questions
What is OCPP solar EV charging integration?
It is the use of the Open Charge Point Protocol to let an energy manager steer an EV charger from live solar surplus. The manager reads PV output and household load, then sends the charger a charging profile that sets a current limit. The charger follows that limit, so the car charges from surplus instead of the grid.
What is the difference between OCPP 1.6, 2.0.1 and 2.1?
OCPP 1.6 (2015) added basic smart charging, OCPP 2.0.1 (2020) added a device model and native ISO 15118 support, and OCPP 2.1 (January 2025) added ISO 15118-20 and bidirectional charging. The Open Charge Alliance says 1.6 and 2.0.1 are not compatible. It says 2.1 is backward compatible with 2.0.1.
Can OCPP charge an EV from solar surplus only?
Yes, if the surplus is large enough. The charging standard IEC 61851 sets a minimum current of 6 A, so surplus charging needs about 1.4 kW on one phase or 4.1 kW on three phases, per evcc documentation. Below that the session pauses. Systems with regulated zero grid export cannot do surplus charging.
What is ISO 15118 Plug and Charge?
Plug and Charge lets a vehicle identify itself to a charger when the cable is plugged in, with no RFID card or app step. The Open Charge Alliance says OCPP 2.0.1 includes native support for ISO 15118 Plug and Charge. OCPP 2.1 adds ISO 15118-20, which includes bidirectional power transfer.
What is a smart charging profile in OCPP?
A charging profile is a message that tells a charger how much current or power to deliver over a schedule. In OCPP 1.6 it has an ID, a stack level, a purpose (ChargePointMaxProfile, TxDefaultProfile or TxProfile), a kind (Absolute, Recurring or Relative) and a schedule in amps or watts. An energy manager updates it as solar output changes.
Does Home Assistant support OCPP for solar charging?
Yes. The open-source Home Assistant OCPP integration says it supports OCPP 1.6j, 2.0.1 and 2.1 (experimental) and has an ocpp.set_charge_rate service that takes a limit in amps. You still need a charger that lets you set its back-end address and an automation that works out the surplus.
Does OCPP remove vendor lock-in for EV chargers?
It helps but does not guarantee it. The Open Charge Alliance says OCPP is open and aims for interoperability across hardware and software. Before you buy, check that the charger lets you set your own back-end address, which OCPP version it runs and whether it is on the Open Charge Alliance certified list.
Where this fits
This article is part of SurgePV's Solar Technology hub, which works through the topic from first principles to the decisions a project team actually has to make.
