Charging sign printed on a parking lot.

EV Charging Reliability: What Is It and How Is It Measured?

It’s clear that the global transition to electric mobility requires the rapid expansion of electric vehicle (EV) charging infrastructure. Despite the emphasis on reliable infrastructure, the actual charging experience for customers often falls short – even when EV charging services boast “99% uptime”. In California last year, for instance, over 20% of public fast EV charging sessions failed.

In order to improve the current level of reliability, it’s critical to start by defining what exactly constitutes a reliable charge and how we measure charging performance.

We’re here to guide you through it all, outlining a collection of charging performance metrics that provide a holistic understanding of EV charging hardware and software. We’ll define the foundations to measuring charging service performance — reliability, availability, and quality of service — and unpack how they are measured and used to take action, ensuring dependable service delivery for a great customer experience.

What is EV charging reliability?

Reliability refers to the ability of a system to consistently perform its intended function without failure or interruption over a given period.

In the context of EV charging, reliability makes up a critical component of overall charging performance. It directly impacts the customer experience, enabling vehicle operators to access a charging service without issues and get the energy they need to go about their day-to-day operations.

How do we measure EV charging performance?

Performance is measured in three key ways. You may have encountered the terms “reliability,” “availability,” and “quality of service” before. Though these terms are often used interchangeably, they have distinct meanings and can be measured in different ways. We break these meanings down below:

How are these EV charging performance metrics related?

Understanding these metrics can be confusing because they are all interconnected. Reliability is about ensuring that when an EV plugs in, the charging process works as expected, forming the foundation of charging. In today’s charging industry, the most frequently utilized metric for time-based availability measurement is “uptime.” However, having a high charging equipment uptime does not necessarily guarantee a positive charging experience. A highly reliable system results in greater uptime, which, in turn, impacts the quality of service. All these factors together determine the overall customer experience.

What needs to be measured?

Each of the areas of measurement above tells us something different about how a charging system performs. Depending on the stakeholder, some metrics might be more important than others. For example, “availability” to a vehicle operator could mean parking space availability for charging, whereas availability to a technician could mean uptime where the EVSE is “up” and functioning.

The metrics used in operations should clearly define how they are calculated, their purpose, and the scope of equipment or processes they measure. Examples of subsystems that can be measured in EV charging operations include network connectivity, EVSE operation, site access and stall supply, as well as non-mechanical services like customer support availability. Because failures can interact with dependent components of a charging system, it can be helpful to establish performance targets for each part of the system to orchestrate a smooth charging experience for customers as a whole.

Are EV charging performance metrics standardized?

At the present time, there is no industry standard for measuring the charging experience. As the industry continues to mature, various methodologies are employed for defining and measuring metrics like uptime. Policy guidance on measuring reliability from National Electric Vehicle Infrastructure (NEVI) Formula Program and the California Energy Commission helps clarify the current direction of the industry.

Whenever you see a performance metric, it’s important to understand the methodology behind how the metric was calculated, and if there are any exclusions that apply.

How do we use these metrics to improve the customer experience?

Performance metrics give us a way to understand overall EV charging performance. Once the system is being measured, the metrics have a broad array of uses to help improve the service experience for customers.

Customer Satisfaction

The customer is the most important part of any charging operation. Performance metrics like uptime affect the charging experience. High uptime and charge success rates contribute to customer satisfaction, while frequent downtime can lead to frustration and disrupted business operations.

24/7 Alerting

Measuring system performance provides a way for charging operators to know when, and often before something goes wrong. Automated fault detection systems enable fast detection to motivate fast action to resolve issues when they arise. This leads to faster resolution times.

Performance Assessment

A combination of metrics is used to assess the charging service operation and where to allocate resources to improve performance.

Contract Agreements

Metrics like uptime are often included in service level agreements (SLAs), which define the expectations and obligations of every party.

Troubleshooting and Maintenance

Metrics can help identify patterns of faults, allowing operators to pinpoint the root causes of failures and plan proactive maintenance accordingly.

Business insights

Metrics on charging performance can also provide insights to customers, enabling them to optimize their operations to save costs or achieve business goals.

Work with Terawatt as we build the future of EV charging

At Terawatt, we aim to use best-in-class performance metrics to build trust and transparency with our customers and deliver top quality charging operations and services.

When things go wrong, we want to hear about them so we can continually improve our operations to meet your business needs. If an issue arises, it provides valuable insights to our fault detection systems so we can proactively identify issues next time.

Terawatt’s ultimate objective is ensuring a best-in-class vehicle charging experience for the customer. When discussing and defining performance metrics with a partner, it’s important to define what the customer needs for their business operation and measure what matters for them.

We hope this blog post helped you learn more about the performance metrics that impact the customer experience, why they matter, and how we can work together to support your charging needs.