Charge RosterStart with the problem, not the software category
“EV charging software” covers several very different jobs.
A workplace may need software to:
- operate and monitor chargers;
- authorize charging sessions;
- meter energy or support billing;
- manage electrical load;
- update charger firmware or diagnose faults;
- reserve a charger at the protocol level;
- show employees when shared charging time is available;
- allocate that time fairly between drivers.
Those jobs can exist in the same system, but they do not have to.
The useful first question is:
Are we trying to operate the charging infrastructure, or coordinate access to it?
What is a CPMS or CSMS?
CPMS usually means charge point management system. OCPP documentation commonly uses Charging Station Management System (CSMS) for the management system that communicates with charging stations.
The Open Charge Alliance defines OCPP as an open protocol for communication between EV charging stations and charging-station management systems. OCPP functionality includes areas such as authorization, transactions, remote control, configuration and, depending on the supported version/profile, smart charging, reservation and device-management capabilities.
Open Charge Alliance: What is OCPP?
Open Charge Alliance: OCPP 2.0.1 certification profiles
A CPMS therefore starts from the charger and charging session. Typical capabilities may include:
- charger connectivity and status;
- user or token authorization;
- charging-session records;
- remote start/stop or other remote commands;
- configuration and diagnostics;
- firmware or device management;
- tariffs, payments or reimbursement workflows;
- smart charging or load-management functions;
- protocol-level reservations where supported.
Exact capabilities vary substantially between products.
What does workplace charger scheduling do?
A workplace scheduling system starts from the people competing for a shared resource.
It answers questions such as:
- Which chargers can this employee use?
- When is charging time available?
- Can the employee reserve 10:00–12:00 before arriving at work?
- How long may one charging turn last?
- What happens when a booking is cancelled?
- Which employee has the next scheduled turn?
- When are requests repeatedly left unserved?
The schedule can exist even if it never sends a command to the charger.
For example, a booking can state that Charger 3 belongs to Alex from 11:00 to 13:00. Employees can see that allocation and plan around it even if the charger itself remains technically unaware of the reservation.
That is the central distinction: allocating access to time is not the same as controlling an electrical charging session.
CPMS vs workplace scheduling at a glance
| Need | Workplace scheduling | CPMS / CSMS |
|---|---|---|
| Show employees bookable charging time | Core job | May support it, product-dependent |
| Reserve a workplace time slot | Core job | May support driver booking or OCPP reservation |
| Apply booking windows and duration rules | Core job | Product-dependent |
| Track schedule conflicts or unmet time requests | Core job | Product-dependent |
| Read charger online/offline status | Not required | Common |
| Read charging sessions or meter values | Not required | Common |
| Communicate with chargers over OCPP | Not required | Common for OCPP-based systems |
| Remote start/stop and charger commands | No | Common |
| Firmware/device management | No | Common |
| Billing, tariffs or reimbursement | No | Often available, product-dependent |
| Smart charging or electrical load control | No | May be available directly or through an EMS/other system |
This is not a product-feature scorecard. CPMS products differ, and some include excellent reservation or workplace modules. The table shows the starting responsibility of each layer.
Is OCPP required for workplace charger booking?
Not necessarily.
OCPP is relevant when software needs to communicate with an OCPP-compatible charging station or CSMS. The Open Charge Alliance describes it as the protocol connecting those systems.
A scheduling-only system can instead coordinate people and time without communicating with the charger at all.
That makes a hardware-independent approach useful when:
- the workplace already has functioning chargers;
- the chargers may come from different vendors;
- replacing the existing CPMS would be disproportionate;
- the unresolved problem is employee access rather than charger operation;
- the workplace wants to prove a scheduling process before investing in deeper integration.
The limitation is equally important: without charger integration, the scheduling layer does not know physical plug state merely because a reservation exists, cannot enforce the reservation electrically and cannot issue charger commands.
Do not call scheduled availability “live charger status” unless the product actually receives that physical status.
OCPP reservations and employee reservations are not identical concepts
OCPP supports reservation-related functionality in supported versions/profiles. That can allow a management system to reserve charging-station capacity for an identifier.
An employee-facing workplace reservation usually includes a broader workflow:
- selecting a workplace site;
- seeing a human-readable calendar;
- choosing a start time and duration;
- applying workplace booking rules;
- cancelling or changing plans;
- understanding fair access across colleagues;
- seeing when demand could not be accommodated.
A CPMS can implement those user-facing workflows, and some do. But the existence of protocol-level reservation functionality does not automatically solve the workplace's allocation policy or employee experience.
The two layers can complement each other.
Where does load management fit?
Load management is another distinct problem.
A workplace may have enough physical charging connectors but insufficient electrical capacity to let every connector draw maximum power simultaneously. Smart charging or an energy-management system can distribute available power across charging sessions.
That question is different from whether two employees both want Charger 2 at 09:00.
Think of the layers this way:
- Scheduling: who gets charging access, and when?
- CPMS/CSMS: what is happening with the chargers and sessions, and what commands should be sent?
- Energy/load management: how should limited electrical power be distributed?
One system can cover more than one layer, but the decisions remain conceptually separate.
When a CPMS is the right starting point
A CPMS should be central when the workplace needs capabilities such as:
- bringing chargers online and monitoring their state;
- remotely controlling sessions;
- centralized RFID/token authorization;
- energy metering and session records;
- tariffs, payment or employee reimbursement;
- maintenance diagnostics;
- firmware/device management;
- smart-charging integration;
- protocol-level enforcement of reservations or access.
If these are the unresolved requirements, buying a scheduling-only layer would not solve the problem.
When a scheduling layer may be enough
A lighter scheduling layer is a reasonable starting point when:
- the chargers already operate satisfactorily;
- employees are competing for access;
- the current process is first-come-first-served, messages, spreadsheets or a shared calendar;
- the workplace needs predictable start/end times;
- it wants one booking process across chargers without changing the charging backend;
- the main decision is whether existing charger time can be shared better before more hardware is added.
This is particularly relevant post-installation: charger infrastructure can be technically complete while day-to-day employee access remains operationally messy.
When you might use both
There is no contradiction in running a CPMS and a workplace scheduling layer together.
For example:
- the CPMS continues handling charger connectivity, sessions, access tokens and maintenance;
- workplace scheduling gives employees the booking experience and allocation rules;
- an integration may be added later if the organisation wants scheduled access to be reflected in charger authorization or physical status.
Whether integration is worth building depends on the value of enforcement and telemetry compared with its cost and complexity.
Do not integrate merely because OCPP exists. Integrate when a specific operational outcome requires it.
Decision checklist
Ask these questions before selecting another EV charging platform:
- Do we already have a CPMS that works?
- Is our problem charger operation or employee access?
- Do we need physical charger status in the booking experience?
- Must a reservation be electronically enforced?
- Do we need payment, billing or reimbursement?
- Do we need load management or only time allocation?
- Do we need remote charger commands?
- Are our chargers from one vendor or several?
- Could a hardware-independent schedule solve the immediate problem?
- Would deeper integration materially improve the employee or administrator experience?
The answer may be CPMS, scheduling, both, or neither.
Where Charge Roster fits
Charge Roster is the workplace scheduling layer in this model. Employees see scheduled availability and reserve charging time; workplaces define sites, chargers and booking rules and can see where the schedule cannot accommodate demand.
Charge Roster does not replace a CPMS, meter energy, control electrical load, remotely operate chargers or claim live physical charger occupancy. It can sit alongside the charger-management system already in use because the core scheduling proposition does not require OCPP integration.