Time-of-Use (ToU) tariffs are pricing structures where the cost of electricity (and therefore EV charging) changes depending on the time of day, day of week, or season. ToU tariffs are designed to reflect grid demand and generation patterns—charging is typically cheaper during off-peak hours and more expensive during peak periods.
In EV charging, ToU tariffs can be applied to:
– The operator’s electricity procurement cost (what the site pays)
– The customer-facing charging price (what drivers or fleets are billed)
– Both, depending on business model and local regulations
Why ToU Tariffs Matter in EV Charging
ToU tariffs are one of the most effective tools for improving site economics and grid impact:
– Reduce energy costs by shifting charging away from expensive peak periods
– Support load management by encouraging off-peak behavior
– Improve grid friendliness and reduce congestion at constrained connections
– Enable fleet depots to charge vehicles overnight at lower cost
– Align charging with higher renewable generation periods (where relevant)
For multi-tenant sites, ToU can also improve fairness by reflecting real energy costs at different times.
How ToU Tariffs Work
A ToU tariff typically defines:
– Time blocks (peak, shoulder, off-peak)
– Different prices for each block (€/kWh or energy cost components)
– Rules for weekends, holidays, or seasonal changes
– Optional demand charge components or maximum demand limits
Charging platforms can apply these time rules automatically, either as customer pricing or as internal cost modeling.
Common ToU Models Used for EV Charging
– Simple peak/off-peak split
Two price levels, typically daytime peak and night off-peak
– Peak/shoulder/off-peak
Three-tier structure for more granular pricing
– Dynamic ToU windows
Prices change based on utility schedules or market signals (still rule-based, not real-time wholesale)
– Fleet-specific ToU schedules
Charging is encouraged during defined “green windows” or low-cost windows aligned with depot operations
Customer-Facing ToU Tariffs vs Operator Cost ToU
Two different ToU layers may exist:
– Operator ToU: site energy cost varies; operator uses this to optimize profitability
– Customer ToU: driver price varies; used to influence charging behavior
An operator can face ToU costs without passing ToU prices to drivers (fixed public pricing), using managed charging internally instead.
Operational Considerations
– ToU works best when paired with managed charging or customer incentives
– Fleet depots can automate charging schedules based on departure readiness
– Public sites may use ToU pricing mainly to reduce congestion or improve margin
– Clear communication is needed to avoid customer confusion and pricing disputes
– ToU pricing should consider idle fee policies and bay turnover rules
Benefits
– Lower energy cost and improved margins
– Reduced peak demand and better compliance with site limits
– Better use of existing grid connection capacity
– Can improve sustainability metrics by shifting load to cleaner grid periods (methodology-dependent)
Limitations and Pitfalls
– Complexity can confuse users if not clearly displayed
– If site load management reduces power during peak times, time-based fees can feel unfair
– ToU incentives may not work if drivers have no flexibility (short dwell times)
– Tariff windows and rates can change, requiring careful configuration and updates
– Roaming pricing may not reflect ToU, creating inconsistencies
Best Practices
– Keep ToU windows simple and easy to explain (especially for public users)
– Use ToU primarily for fleets and workplaces where scheduling is feasible
– Pair ToU with automation: charge-by-departure scheduling and power caps
– Provide transparent price display and receipts showing the applied ToU block
– Track impact: off-peak share, peak demand reduction, cost savings
Related Glossary Terms
Time-based Pricing
Time-based Billing
Tariff Structures
Tariffs
Managed Charging
Load Management
Maximum Site Demand Limit
Off-peak Charging
Peak Demand
Peak Shaving