What is charging uptime?
Charging uptime is the percentage of time a charge point, or an individual charging port on it, is operational and capable of delivering electricity during a defined period. It is a key performance indicator (KPI) used to measure the reliability of EV charging infrastructure.
Charging uptime helps charge point operators (CPOs) monitor network performance, identify recurring faults and demonstrate compliance with regulatory requirements.
There is no single global standard for measuring uptime. Regulations differ in how they define operational status, which outages can be excluded and whether uptime is measured per charging port or across an entire network. An uptime clause in a contract or SLA therefore has to state the unit (port, site or network), the period, the exclusions and the data source.
How is charging uptime calculated?
Charging uptime is generally calculated by comparing the time a charger is operational with the total time included in the measurement period.
Uptime (%) = (Operational time ÷ Total measured time) × 100
For example, if a charging port operates for 720 hours during a 730-hour measurement period, its uptime is approximately 98.6%.
The calculation typically involves:
- Monitoring charger status: A charge point management system (CPMS) records the status each charger reports, commonly through OCPP.
- Identifying downtime: The CPMS logs every period when a charger cannot provide its intended service.
- Applying exclusions: Depending on the applicable standard, certain interruptions, such as utility power failures or scheduled maintenance, are excluded.
- Calculating uptime: The operator totals operational and downtime minutes over the reporting period and applies the formula.
The exact calculation depends on the applicable regulations. The US NEVI program, for example, deducts excluded downtime from recorded outage minutes before calculating the annual figure. Its exclusions are utility power interruptions, vehicle faults, scheduled maintenance, vandalism, natural disasters and hours outside the station’s opening times, provided the operator can show the port would otherwise have worked.
Uptime vs. availability vs. charging reliability
Uptime, availability and charging reliability measure three different things.
- Uptime measures how consistently a charging port remains operational over time.
- Availability is a port’s live state at one moment: free, in use or reserved. Operational status says whether it is working or out of service. Both describe a single moment, not performance over time.
- Charging reliability describes whether a driver can successfully start and complete a charging session. (The UK regulations use the same word for their status-based 99% rule, described below.)
A charger can report high uptime while drivers still run into payment faults, failed session starts or interrupted sessions. Uptime is usually calculated from the status each charger reports to the platform over OCPP, and a charger reports itself available when its own electronics see no fault. A broken payment terminal, a rejected authorization or a failed handshake with the vehicle can stop a session while the port still counts as up. That is why CPOs track charging success rates alongside uptime: together they show how reliable the network is for the people using it.
What are the regulatory uptime requirements for EV chargers?
Uptime requirements differ across markets. US NEVI requires greater than 97% annual uptime per port, California requires 97% for publicly or ratepayer-funded DC fast charging ports, and the UK requires 99% average network reliability for rapid chargers. EU AFIR sets no fixed uptime percentage.
| Regulation | Uptime requirement |
|---|---|
| US NEVI (National Electric Vehicle Infrastructure) minimum standards | Greater than 97% annual uptime per charging port, calculated monthly over the previous 12 months |
| UK Public Charge Point Regulations 2023 (PCPR) | At least 99% average annual reliability across an operator’s network of public rapid charge points (50 kW and above), with annual reporting required |
| California EV Charger Data and Reliability Standards (CEC) | 97% uptime per port for publicly or ratepayer-funded DC fast charging ports installed on or after 1 January 2024, subject to specified exclusions |
| EU Alternative Fuels Infrastructure Regulation (AFIR) | No fixed uptime percentage; operators of publicly accessible charge points must make dynamic data, including operational status and availability, accessible (Article 20), in the format set by Implementing Regulation (EU) 2025/655 |
They also count differently. NEVI counts a port as up only when its hardware and software are online and it can deliver electricity at the required minimum power. The UK uses the status the operator reports: available, charging and reserved count as reliable; inoperative and out of order do not. A charging network meeting one standard does not automatically meet another.
Why is charging uptime important for operators?
High uptime keeps charging ports available to sell sessions. Unplanned downtime means missed sessions, higher maintenance costs and a poorer driver experience, and for operators subject to regulatory uptime targets it also creates compliance risk.
Depending on how it is measured, uptime can miss payment failures, failed charging attempts and reduced charging speeds on a port that shows as operational. Tracking it alongside session success rate, fault frequency and repair times fills those gaps.
How AMPECO supports charging uptime tracking
AMPECO’s EV charging management platform provides uptime monitoring at charge point level and for each EVSE, the part of a charge point that serves one vehicle at a time.
Operators can analyze uptime over today, month-to-date, quarter-to-date and year-to-date periods, and over rolling 30-, 60- and 365-day windows. The platform also supports operator-specific calculation formulas for regional requirements such as the UK PCPR, US NEVI and Australia’s minimum operating standards for government-supported public charging.
The platform’s remote management and maintenance tools detect faults, monitor charge point status and run automated recovery actions where the hardware supports them.
The uptime tracking and reporting post describes the uptime cards and their calculation models in more detail.
Frequently asked questions
What is a good uptime percentage for EV chargers?
Regulatory benchmarks include greater than 97% per charging port under US NEVI standards and at least 99% average network reliability under UK regulations for rapid chargers. Compare figures only when they were measured the same way: a 97% NEVI per-port figure and a 99% UK network average are not the same number.
Can an EV charger report high uptime but still fail to charge vehicles?
Yes. A charger can report an operational status while drivers cannot start or complete a session. Tracking charging success rates alongside uptime shows the problems that status data alone misses.
What causes EV charger downtime?
Common causes are unresponsive screens, payment faults, charge initiation errors, lost network connections and broken connectors. Utility outages, vandalism and scheduled maintenance also take ports offline, which is why NEVI lists them as excludable causes.
Related terms
- CPMS (Charge Point Management System)
- OCPP (Open Charge Point Protocol)
- EVSE
- CPO
- En-Route EV Charging
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