A charger that does not work costs more than one that was never installed: it strands drivers and erodes confidence in electric vehicles. Reliability is the most common complaint about public charging, and it is an operations problem more than a hardware problem.

How uptime is measured

For chargers funded under the federal NEVI program, 23 CFR 680.116 requires each charging port to maintain average annual uptime greater than 97 percent. The rule defines how to calculate it: time the port is available as a share of total time, with narrow exclusions for things outside the operator’s control, such as utility outages, vandalism and scheduled maintenance.

Two details in that definition matter:

  • Uptime is per port, not per site. A four-port site with one dead port is not “up”.
  • A port that is powered but cannot complete a session (for example, because payment or the network back end has failed) is not available.

97 percent still allows about 11 days of downtime per port per year. Well-run networks aim higher.

Why chargers fail

Common causes, roughly in order of how often field technicians see them:

  1. Connectivity and back-end faults. Lost cellular signal, expired certificates, payment processor errors and network configuration problems.
  2. Cable and connector damage. Cables run over or dropped, connectors with damaged pins, and cable-management failures.
  3. Payment hardware. Card readers are exposed, heavily used components.
  4. Power electronics in DC fast chargers: power modules, contactors and cooling fans.
  5. Firmware defects and incompatibilities between vehicles and chargers.
  6. Site issues. Blocked or ICE’d spaces, tripped breakers and utility-side problems.

What keeps a site working

  • Remote monitoring with alerting. OCPP gives the operator real-time status. Someone has to watch it and act on it.
  • Preventive maintenance on a schedule: connector inspection, filter and fan service, torque checks and firmware updates.
  • Fast break-fix response. Define response and repair times in the service contract, and stock spare parts for the components that fail most.
  • Qualified technicians. Work on EVSE is electrical work. Use technicians trained on the specific equipment.
  • Driver feedback loops. Driver reports through apps and signage are often the first sign of a problem that monitoring does not see, such as a damaged cable or a blocked space.

Questions to ask a network or maintenance provider

  • How do you define and report uptime, per port, and against which exclusions?
  • What is your guaranteed response time and time to repair?
  • Who stocks parts, and where?
  • Will you share raw session and fault data, not just summaries?