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EV Charging KPIs: Definitions, Formulas, and What Charging Software Should Report

Last reviewed: September 2026. Regulatory references reflect 23 CFR 680 and California's EV charger reliability regulations as published at that date.
EV charging KPI glossary with formulas for uptime, utilization and sessions per port per day
Every EV charging operator eventually asks the same question: is this network performing? The answer depends on a short list of EV charging KPIs, and on whether your charging software captures the data behind them. Uptime, utilization and sessions per port per day sound simple. In practice, two operators can report very different numbers for the same site because they count ports, hours and outages differently.

This guide gives you precise definitions and formulas for eight core KPIs, the minimum feature set charging software needs to calculate them, and the structure of a monthly operations report. Every formula is written so it can be checked against raw data.
Key takeaways
  • Charging software is the source of every KPI. If it does not record port status history, session records, meter values and transactions per port, the numbers cannot be audited.
  • Uptime, availability and charge success rate answer different questions. A port can report 99% uptime and still fail drivers.
  • Utilization has several valid definitions (active charging time, plugged-in time, energy versus capacity). State which one you use.
  • Before comparing any KPI across sites or vendors, compare the denominators: port or charger, 24 hours or operating hours, and which outages are excluded.

What is charging software?

Charging software is the management layer that connects to EV chargers over a network and lets an operator monitor, control, price and report on them. In commercial charging, it usually means a charging station management system (CSMS): the back office that chargers communicate with, typically over OCPP, and the system of record for every session, status change and energy reading behind your KPIs.

You will see the same category described as EV charging software, charging station software, an EV charging management system, an EV charging platform, a CSMS or a CPMS. The two acronyms come from different versions of the Open Charge Point Protocol. OCPP 1.6 used the terms charge point and central system, which is where the market term charge point management system (CPMS) comes from. OCPP 2.0.1 renamed them charging station and charging station management system (CSMS). In practice, CSMS and CPMS describe the same layer.

Keep three layers separate: charger firmware controls power delivery on the hardware, the CSMS manages chargers remotely and holds the operational data, and driver apps and roaming connections let drivers find, start and pay for sessions. The protocols differ by job: OCPP connects chargers to the CSMS, while OCPI (Open Charge Point Interface, maintained by the EVRoaming Foundation) connects charge point operators with eMobility service providers so drivers can use chargers across networks. KPIs are calculated in the CSMS layer, so its data quality matters more than its dashboard design.

For a full definition of the category and a vendor checklist, see our guide to EV charging management software. For how OCPP backends differ from CPO platforms and charger clouds, see OCPP platform explained.

Terms used in this guide

KPIs break when "charger," "station," "port" and "connector" are used as synonyms. This guide uses them as follows.
Unless stated otherwise, every KPI below is calculated per port, because a dual-port charger with one broken port is not fully working, and counting connectors instead of ports inflates the denominator.

The minimum feature set: what charging software must capture

Most feature lists describe what software can do. A more useful test for buyers is what it records. Every KPI in this guide is calculated from four raw data streams: port status history, session records, meter values and payment transactions. If a platform cannot capture those streams consistently and let you export them, its dashboards are summaries you cannot verify.

The table below separates the capabilities a serious commercial deployment should treat as minimum requirements from those that depend on the use case.
Underneath all of it sits the charger protocol. OCPP is what makes hardware-agnostic management possible, and the version matters: many installed chargers still run OCPP 1.6J, while newer programs, including California's reliability regulations, are moving to certified OCPP 2.0.1. Reporting is also only as useful as its dimensions: at minimum, by network, site, charger, port, user group and time (day, week and hour of day).

EV charging KPI glossary

These eight KPIs cover reliability, usage, financial performance and service for most operator types. Each is defined per port, and each formula uses data a CSMS should already hold.
Port-days in service is the sum of the days each port was installed and commissioned during the period. It is the denominator that keeps new, removed or decommissioned ports from distorting per-port averages.
Before comparing KPIs, compare the denominators
  • Unit: per port, per charger, per site or per network.
  • Time base: 24 hours a day or posted operating hours.
  • Exclusions: which outages are removed from uptime, and whether they are capped.
  • Period: calendar month, calendar year or trailing 12 months.
  • Session rules: whether failed attempts, very short sessions or test sessions are counted.
  • Data source: charger-reported meter values, a separate revenue-grade meter or estimates.
Two sites can both claim "98% uptime" and mean different things. If any of these six choices differ, the comparison is not valid.

1. Port uptime

Port uptime is the percentage of time a charging port was operational, meaning able to charge a vehicle or already charging one, after approved exclusions are removed.
Port uptime (%) = (Total minutes in period - (Outage minutes - Excluded outage minutes)) ÷ Total minutes in period × 100
What it tells you: whether the hardware, software and connectivity behind a port were working.

Important caveat: uptime is the KPI most often defined by regulation, and the definitions are close but not identical.

  • Federal NEVI standard. 23 CFR 680.116 requires each NEVI-funded charging port to have an average annual uptime greater than 97%. A port is "up" when its hardware and software are both online and available for use, or in use, and it successfully dispenses electricity at the required minimum power level. Uptime is calculated monthly over the previous twelve months (525,600 minutes). Excluded outages are those outside the operator's control: electric utility service interruptions, failure to charge due to the vehicle, scheduled maintenance, vandalism, natural disasters, and hours outside the station's identified hours of operation.
  • California. The California Energy Commission's EV charger reliability and data regulations also measure uptime per port, report it in semiannual periods, and set a 97% minimum annual average for publicly or ratepayer funded chargers installed on or after January 1, 2024. Level 2, fleet and private residential chargers are exempt, so in practice it applies to funded DC fast chargers. California caps some exclusions: preventive maintenance counts only up to 72 hours per 12 months when scheduled at least two weeks ahead, and vandalism or theft up to 10 days per incident. Network communication outages are excluded only if the charger defaults to free charging. Amendments were under review in September 2026, so check the current text before relying on specific caps.
  • Commercial contracts often differ again, for example per charger instead of per port, or with broader exclusions. Ask for the formula in writing.

Whatever standard applies, pin down five things before accepting an uptime figure: the numerator (what counts as up), the denominator (24/7 or operating hours), the exclusions and their caps, the measurement interval, and whether it is measured per port or per charger. The Open Charge Alliance recommends calculating uptime per EVSE rather than per charging station or location, then aggregating.
“
EXAMPLE

A port operates 24/7 during a 30-day month: 43,200 minutes. It records 1,000 minutes of outage, of which 400 minutes were a documented utility outage.

Port uptime = (43,200 - (1,000 - 400)) ÷ 43,200 × 100 = 98.6%

Aggregation matters. At a four-port site where three ports ran at 100% and one was faulted for 6 days (80% uptime), average port uptime is 95%. If that faulted port sits on a dual-port charger and the charger is counted as "up" while either port works, charger-level uptime reads 100%.
For who is accountable when uptime drops, and what an uptime SLA should include, see EV charging station software vs. network provider.

2. Charge success rate

Charge success rate is the percentage of charge attempts that start delivering energy and end normally, without the driver needing to retry or intervene.
Charge success rate (%) = Successful sessions ÷ Charge attempts × 100
What it tells you: whether drivers actually get a charge when they try, which uptime alone cannot show.

Important caveat: the denominator is the hard part. Software only sees attempts that generate data, so a card reader failure that never reaches the CSMS, or a driver who gives up before plugging in, may not be counted. Operators also differ on retries: first-attempt success counts a retried session as a failure, while eventual success does not. The ChargeX Consortium (Idaho, Argonne and National Renewable Energy Laboratories) published a KPI implementation guide that defines charge start success, charge end success and session success using specific OCPP messages. It is the most rigorous public reference for this metric.

The gap between uptime and success is real. ChargerHelp's 2025 EV Charging Reliability Report, based on more than 100,000 sessions across 2,400 chargers, found reported uptime of 98.7% to 99.9% while only 71% of charging attempts succeeded.
“
EXAMPLE

A site logs 1,120 charge attempts in a month. 1,035 delivered energy and ended normally.

Charge success rate = 1,035 ÷ 1,120 × 100 = 92.4%

3. Utilization

EV charger utilization is the percentage of a port's available time spent charging vehicles. This guide uses time utilization: active charging hours divided by operating hours.
Time utilization (%) = Active charging hours ÷ Operating hours × 100
What it tells you: how much of the capacity you built is being used, and whether a site needs more ports or fewer.

Important caveat: there is no single industry definition. NREL's analysis of the EV WATTS dataset notes that "there is a multitude of possible calculations for utilization" (NREL, 2023), and Paren's fast charging reports count both successful and unsuccessful charging activity during open hours. Two related versions are worth tracking alongside time utilization:
Occupancy (%) = Plugged-in hours ÷ Operating hours × 100

Energy utilization (%) = kWh delivered ÷ (Port rated kW × Operating hours) × 100
Occupancy is higher than time utilization whenever vehicles stay plugged in after charging. Energy utilization falls when load management limits power, even if the port is busy. That is why a multifamily garage with shared circuits can show high occupancy and modest energy utilization at the same time.
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EXAMPLE

A 7.2 kW Level 2 port is accessible 24/7 for 30 days (720 hours). Vehicles were plugged in for 180 hours and actively charging for 108 hours, delivering 700 kWh.

Time utilization = 108 ÷ 720 × 100 = 15.0%

Occupancy = 180 ÷ 720 × 100 = 25.0%

Energy utilization = 700 ÷ (7.2 × 720) × 100 = 13.5%

Now change only the denominator. If the same port sits in a workplace lot open 10 hours a day on 22 weekdays (220 operating hours), the same 108 charging hours give a time utilization of 49.1%.
What is a good utilization rate? There is no universal benchmark: a depot, an apartment garage and a highway fast charging site are built for different jobs, and published figures only mean something with their definition and scope attached. For example, Paren reported average U.S. DC fast charging utilization of 16.4% in Q4 2025 under its own definition (Paren, January 2026). That figure says nothing about Level 2 workplace or multifamily charging.

4. Sessions per port per day

Sessions per port per day is the average number of charging sessions each in-service port handled per day during a period.
Sessions per port per day = Total sessions ÷ Port-days in service
If the number of ports did not change during the period, this simplifies to Total sessions ÷ (Ports × Days).

What it tells you: demand and turnover. It is the quickest way to compare activity across sites of different sizes.

What it does not tell you: how much energy was delivered, how much revenue was earned, whether demand was unmet because drivers found ports occupied, or whether sessions were short top-ups or overnight stays. Read it together with energy per port per day and session duration.

Important caveat: decide whether a session must deliver energy to count. This guide counts only sessions that delivered energy and reports failed attempts in the charge success rate. Ranges are wide even within one segment: Paren's 2025 data showed state averages for DC fast charging from 1.1 sessions per port per day in Alaska to 12.3 in the District of Columbia.
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EXAMPLE

A site has 12 ports. Eleven were in service all 30 days of the month; one was commissioned on day 16 and was in service for 15 days. Port-days in service = (11 × 30) + 15 = 345. The site logged 1,035 sessions.

Sessions per port per day = 1,035 ÷ 345 = 3.0

Dividing by 12 ports × 30 days instead would give 2.9 and understate demand on the ports that were actually available.

5. Energy delivered per port per day

Energy delivered per port per day is the average number of kilowatt-hours each in-service port delivered per day.
kWh per port per day = Total kWh delivered ÷ Port-days in service
What it tells you: throughput. It drives energy cost, revenue on kWh pricing and electrical capacity planning, and it is the unit NREL used to report public charging utilization in the EV WATTS analysis.

Important caveat: confirm the data source (charger-reported meter values, a separate revenue-grade meter, or estimates), and do not compare Level 2 and DC fast charging ports on this metric without separating them.
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EXAMPLE

The same 12-port site delivered 20,700 kWh over 345 port-days.

kWh per port per day = 20,700 ÷ 345 = 60 kWh

6. Average session duration

Average session duration is the average time a vehicle stays plugged into a port per session, reported alongside active charging time so idle time is visible.
Average session duration (min) = Total plugged-in minutes ÷ Total sessions

Idle time (min) = Plugged-in minutes - Active charging minutes
What it tells you: turnover, and whether fully charged vehicles are blocking ports. This is often the metric behind idle fee decisions at workplaces and multifamily properties.

Important caveat: long overnight sessions pull the average up, so report the median as well. Also confirm session boundaries: plug-in to unplug and authorization to stop can produce different durations.
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EXAMPLE

Three sessions last 45, 60 and 660 minutes.

Average session duration = 765 ÷ 3 = 255 minutes. The median is 60 minutes.

7. Revenue per port

Revenue per port is the net charging revenue earned per in-service port over a period.
Revenue per port ($) = Net charging revenue ÷ Ports in service

Revenue per kWh ($) = Net charging revenue ÷ Total kWh delivered
What it tells you: whether pricing and demand are producing a return on each installed port.

Important caveat: state what "net" removes: payment processing fees, refunds, taxes, revenue share and whether idle fees are included. For fleets and other private charging where drivers do not pay, replace this KPI with energy cost per kWh (Total energy cost ÷ Total kWh delivered), and state whether demand charges are included.

8. Mean time to repair (MTTR)

Mean time to repair is the average time from when a port fault is detected to when the port is verified back in service.
MTTR (hours) = Total repair hours for resolved faults ÷ Number of resolved faults
What it tells you: how quickly your operations and service partners restore capacity once something breaks.

Important caveat: define when the clock starts (fault detected by software, reported by a driver, or ticket opened) and when it stops (ticket closed, or port back to Available with a successful session). MTTR is an industry KPI rather than a regulatory term. Report the median and the age of open tickets too, because one long outage can hide behind a healthy average.
“
EXAMPLE

Three faults were resolved in 4, 20 and 72 hours.

MTTR = 96 ÷ 3 = 32 hours. The median is 20 hours.

Uptime vs. availability vs. charge success rate

Uptime measures whether a port could charge a vehicle. Availability measures whether it was free for the next driver. Under both the federal NEVI rule and California's regulations, a port that is in use counts as up. So a busy, healthy port can show high uptime and low availability, and a port that reports as online but fails sessions can still report high uptime alongside a poor charge success rate.
Availability (%) = Minutes in Available status ÷ Operating minutes × 100
In OCPP 2.0.1, connectors report one of five statuses: Available, Occupied, Reserved, Unavailable or Faulted. Uptime typically treats Available, Occupied and Reserved as up; availability counts only Available. One warning for contracts: some SLAs use "availability" as a synonym for uptime. If a vendor quotes an availability figure, ask which definition it follows.

Which KPIs matter most by operator type

All eight KPIs are worth tracking, but different operators should lead with different ones.
One fleet-specific note: the KPI fleet managers care about most, vehicles charged to target by departure, usually needs vehicle or telematics data. Charging software alone may only see energy delivered, so confirm how the two systems connect. For more detail by vertical, see our guides to EV charging solutions for apartments and fleet electrification software.

What should an EV charging operations report include?

A monthly EV charging operations report should cover five areas: a portfolio snapshot, reliability, usage, financial performance and service. Each KPI should be shown against the prior month and a target, with its definition stated once, and the report should end with specific actions.

  1. Portfolio snapshot: sites, chargers and ports in service; ports added or removed; port-days in the period.
  2. Reliability: port uptime with exclusions listed, charge success rate, ports below target, and the most frequent fault codes.
  3. Usage: sessions, sessions per port per day, kWh delivered, kWh per port per day, utilization (with its definition), and average and median session duration.
  4. Financial: net revenue, revenue per port, revenue per kWh, energy cost per kWh and refunds.
  5. Service: tickets opened and closed, MTTR, open tickets past SLA, and remote vs. on-site resolutions.
  6. Actions: the three to five decisions the data supports, such as repairs, pricing changes, load settings or expansion.
Keep definitions fixed from month to month and attach a port-level appendix, so a site average never hides a single failing port. If you operate NEVI-funded or California-funded chargers, a consistent monthly report also makes compliance reporting easier: NEVI recipients submit session, energy, uptime and outage data quarterly under 23 CFR 680.112, and California requires semiannual reports.
Want a sample monthly report?
We have put these KPIs into a ready-to-use monthly operations report: portfolio, reliability, usage, financial and service sections, with the definition of every metric built in. Request a copy and we will send it to you, or book a demo to see how Epic reports this data.
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How to evaluate charging software using these KPIs

A dashboard can make any network look healthy. When you evaluate charging software, or review your provider before a renewal, ask for the data behind the charts:

  1. Show the uptime calculation for one port: numerator, denominator, exclusions and period.
  2. Export last month's raw status history for that port.
  3. Show failed charge attempts with stop reasons or error codes, not only completed sessions.
  4. Let us choose the time base for utilization: 24 hours or operating hours.
  5. Report at port level and roll up to charger, site and network without changing definitions.
  6. Export sessions with start and end time, plugged-in vs. charging time, kWh and revenue, in CSV and via API.
  7. Link tickets to specific chargers with open and resolved timestamps, so MTTR can be calculated.
  8. Confirm in the contract that we own the data and can export full history if we switch providers.
If a vendor cannot do the first three, its uptime and success figures are claims rather than measurements. For contract terms, renewal red flags and data ownership questions, see our EV charging software evaluation and renewal checklist.

How Epic Charging handles this data

Epic Charging's charging station management system is OCPP-based and certified to OCPP 2.0.1 in the Open Charge Alliance certification program (Core and Advanced Security), and it works with chargers from more than 125 brands. In the Epic dashboard, operators can generate session reports filtered by location, charger, status and date range, run an uptime report that defaults to the previous twelve months, export 15-minute interval data as CSV, track tickets linked to specific chargers, and set power limits for charger groups. Teams that want the same data in their own BI, billing or fleet systems can use the Epic API.

FAQs

Get the sample report
Request our sample monthly EV charging operations report, or book a demo and ask us to walk through the eight checks above in Epic: the uptime calculation, raw status history, failed attempts, exports and API access.
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Sources and further reading