kWh-based billing is an EV charging pricing method where the customer pays based on the amount of electrical energy delivered during a session, measured in kilowatt-hours (kWh). It is widely considered the most transparent and fair billing model because it directly reflects what the driver consumes, regardless of vehicle charging speed.
What Is kWh-Based Billing?
With kWh-based billing, the total price is calculated from:
– Energy delivered (kWh) × price per kWh
Optional add-ons can include:
– A session start fee
– Time-based components (e.g., parking or idle fees)
– Peak/off-peak pricing differences under time-of-use (TOU) tariffs
– Discounts for memberships or fleets
The core billing unit remains the metered energy delivered.
Why kWh-Based Billing Matters
kWh-based billing is preferred in many markets because it:
– Is easy for customers to understand and compare across networks
– Charges fairly across different EV models and charging curves
– Avoids penalizing vehicles that charge more slowly
– Aligns price with actual electricity cost and consumption
– Supports transparent consumer protection requirements in public charging
For CPOs and hosts, it also improves pricing credibility and reduces complaints about unfair time-based charging.
How kWh-Based Billing Works
A typical kWh-based billing flow:
– The charger measures delivered energy using an internal meter or an external certified meter
– The CPMS records session start/stop and total kWh delivered
– A tariff engine applies the per-kWh price (and any additional components)
– The driver receives a receipt/invoice with kWh, price, VAT, and totals
– For roaming sessions, kWh data is included in the CDR for settlement (interoperability billing)
Accurate metering and consistent data handling are crucial.
Metering and Compliance Considerations
In many jurisdictions, billing based on energy requires:
– Legally compliant metering (often MID metering in EU contexts)
– Calibration and sealing requirements (market dependent)
– Clear display of unit price and total cost before or at session start
– Data retention and auditability for billing disputes
Where billing-grade requirements apply, non-certified meters may be acceptable for internal reporting but not for regulated resale billing.
kWh-Based Billing vs Time-Based Billing
These models produce different incentives:
– kWh-based billing charges for energy delivered and is generally fair across vehicles
– Time-based billing charges for time connected and encourages turnover but can penalize slow-charging cars
Many networks combine both:
– kWh-based energy price during active charging
– Time-based idle fees after charging completes to prevent bay blocking
Operational Considerations
For CPOs, successful kWh-based billing depends on:
– Meter accuracy and correct handling of rounding rules
– Stable timestamps and session integrity (avoid “stuck sessions”)
– Clear tariff versioning and price transparency at the point of charge
– Reconciliation processes for missing or abnormal session records
– Consistent VAT and invoicing workflows, especially in cross-border contexts
Related Glossary Terms
Tariff Management
MID Metering
Charge Detail Record (CDR)
Interoperability Billing
Roaming
CPMS
Ad-hoc Payment
Idle Fees
Time-of-Use (TOU) Tariffs
Session Fee