Time-based billing is an EV charging pricing model where a customer is charged based on the time their vehicle is connected or charging—typically billed per minute or per hour—rather than based on energy delivered (kWh). It is used in public, workplace, and some fleet contexts to encourage bay turnover and manage congestion.
Time-based billing can apply to:
– Charging time only (when power is being delivered)
– Plug-in time (from plug-in until unplug)
– Post-charge time (as an idle fee after charging completes)
Why Time-based Billing Is Used
Time-based billing is often chosen to:
– Improve bay turnover at busy sites
– Reduce blocking behavior where vehicles stay connected after charging is complete
– Simplify pricing when energy metering rules make per-kWh billing more complex
– Align pricing with parking-time value in high-demand locations
– Create predictable revenue per occupied bay (site economics)
It is especially common where charging speed varies by vehicle and where congestion management is a priority.
How Time-based Billing Works
A typical time-based billing setup includes:
– A defined tariff rate (e.g., €/min or €/hour)
– Clear rules for when billing starts and stops
– Optional grace periods (for plug-in setup or post-charge departure)
– Optional caps or step changes (higher rates after a set time)
– Different rules by user group (public vs fleet vs subscription users)
Time-based billing is often combined with other tariff components as a hybrid structure.
Common Variants of Time-based Billing
Time-based billing is commonly implemented in these forms:
– Charging-time billing
Only time while energy is actively delivered is billed
– Plugged-in billing
All time from plug-in to unplug is billed, even if charging has ended
– Idle fee billing
Time-based fees only after charging completes, often after a grace period (idle fee policy)
– Tiered time tariffs
Rate increases after a set threshold to discourage long occupancy
Benefits of Time-based Billing
– Encourages turnover and reduces bay blocking
– Helps manage congestion at destination sites (retail, city centers)
– Simple to understand when clearly defined on signage/app
– Reduces dependence on certified energy metering in some setups
– Can be used to align charging and parking economics
Limitations and Fairness Considerations
Time-based billing can be perceived as unfair because charging power is not constant:
– Vehicles with lower onboard charger limits may pay more for the same kWh
– Charging naturally slows at high State of Charge (SoC), increasing cost per kWh
– Battery temperature and temperature derating can reduce power and raise cost per kWh
– Site load management can reduce available power, again increasing cost per kWh
– Users may feel penalized for factors outside their control
These issues are why many operators prefer per-kWh billing where feasible, using time-based fees mainly for idle management.
Best Practices
– Make start/stop rules transparent (charging time vs plug-in time)
– Use time-based fees primarily as idle fees to protect availability
– Apply grace periods and clear escalation to avoid customer backlash
– Segment by site type: busy public sites may need stronger turnover rules
– Monitor complaints, utilization, and throughput to tune tariff settings
– Ensure time billing aligns with site power limits and user expectations
Related Glossary Terms
Per-minute Billing
Per-kWh Billing
Idle Fee Policy
Tariff Structures
Tariffs
State of Charge (SoC)
Load Management
Temperature Derating
Pay-as-you-go Charging