Availability rate is a percentage KPI that shows how often an EV charger (or charging network) is operational and usable over a defined time period. It is one of the most important reliability metrics for CPOs, site owners, fleets, and public charging programs because it directly reflects whether drivers can successfully charge upon arrival.
What Is Availability Rate?
Availability rate quantifies charger readiness as a percentage:
– Availability rate (%) = (Usable operational time ÷ Total time in period) × 100
A charger is typically counted as “available” when it is ready to start a session and deliver energy without critical faults. Many operators calculate availability at the connector level (most accurate), then roll it up to the charger, site, and network levels.
Why Availability Rate Matters in EV Infrastructure
Availability rate is a commercial and service-quality KPI, not just a technical metric. It affects:
– Driver trust, repeat usage, and station reputation
– Revenue, utilization, and ROI per charger
– Compliance with SLAs, tenders, and public funding requirements
– Fleet operations where vehicles must be ready on schedule
– Maintenance planning and spare parts strategy
High availability rate is especially critical for public charging, where a single failure can strand users and damage brand perception.
How Availability Rate Is Measured
The availability rate is calculated over a defined window (daily, monthly, or quarterly). Operators typically rely on charger status and event logs via OCPP and backend monitoring rules.
Common measurement approaches include:
– Connector availability: Each outlet is tracked independently
– Charger availability: One status for the whole unit (less precise for dual outlets)
– Site availability: Aggregated across all connectors on the site
– Network availability: Portfolio-level KPI across all sites
To avoid misleading results, many systems define which states count as “available” vs “unavailable,” for example:
– Available: idle/ready, preparing, charging (depends on definition), finishing
– Unavailable: faulted, unavailable, out of service, blocked by critical error
Availability Rate vs Utilization
Availability rate is often confused with utilization, but they measure different things:
– Availability rate: “Is the charger working and ready?”
– Utilization: “How much is the charger being used to deliver energy?”
A charger can have high availability but low utilization if demand is low, or low availability but high utilization if it is heavily used but frequently failing.
Common Causes of Reduced Availability Rate
– Hardware faults (connector wear, relays/contactors, cable damage)
– Electrical issues (earthing, RCD trips, unstable supply, overload trips)
– Communication and backend issues (SIM/network downtime, server outages)
– Payment/authentication failures (RFID/app/QR flow problems)
– Environmental damage (water ingress, vandalism, extreme temperatures)
– Poor site operation (blocked bays, lack of maintenance, slow repairs)
How to Improve Availability Rate
Operators typically raise availability rate through:
– Proactive monitoring and automated fault alerts
– Preventive maintenance and periodic inspections
– Faster MTTR through local service partners and spare parts availability
– Robust installation design and commissioning checks
– Redundant connectivity (Ethernet + cellular)
– Smart load management to prevent overload shutdowns
– Controlled firmware updates and rollback procedures
Key Benefits of a High Availability Rate
– More successful charging sessions and higher revenue
– Better driver experience and stronger network ratings
– Easier compliance with SLAs and procurement requirements
– Lower operational costs over time through fewer emergencies
– Stronger data quality for billing, reporting, and reconciliation
Limitations to Consider
– Definitions vary: some operators count “charging” time as available, others don’t
– Backend-reported status may not capture real user failures (intermittent faults, payment errors)
– Site factors (ICEing, blocked bays) can reduce real-world availability without showing as a technical outage
– Dual-outlet chargers need connector-level tracking to avoid overstating availability
Related Glossary Terms
Availability
Uptime
Service Level Agreement (SLA)
OCPP
MTBF
MTTR
Remote Monitoring
Preventive Maintenance
Charging Session Failure Rate
Fault Diagnostics