Tariffs: pricing as data

The structure

Three nested concepts, and the nesting is the whole model.

The four component types

A single tariff can carry several types at once — a flat connection fee, an energy rate, and an idle fee that begins after charging completes. That is normal, and it is why a driver's final bill rarely equals kWh multiplied by a headline rate.

Restrictions decide which element applies

Restrictions are what turn a static price list into time-of-use, power-tiered, or customer-specific pricing.

Example: peak/off-peak energy tariff

{
  "country_code": "IN", "party_id": "EFI",
  "id": "TRF-DC-STD",
  "currency": "INR",
  "type": "REGULAR",
  "elements": [
    {
      "price_components": [
        { "type": "ENERGY", "price": 22.00, "step_size": 1 }
      ],
      "restrictions": { "start_time": "09:00", "end_time": "22:00" }
    },
    {
      "price_components": [
        { "type": "ENERGY", "price": 14.50, "step_size": 1 }
      ],
      "restrictions": { "start_time": "22:00", "end_time": "09:00" }
    },
    {
      "price_components": [
        { "type": "PARKING_TIME", "price": 120.00, "step_size": 300 }
      ],
      "restrictions": { "min_duration": 2700 }
    }
  ],
  "last_updated": "2026-08-01T00:00:00Z"
}

Reading it: 22 INR/kWh during the day, 14.50 overnight, and after 45 minutes connected an idle fee of 120 INR per hour billed in 5-minute blocks. A session spanning 22:00 crosses the boundary and is billed at both rates, which is exactly why the CDR splits into charging periods.

step_size is where the money leaks

step_size is the rounding unit, and it is the least understood field in the module. It defines the increment in which a dimension is billed.

Rounding is upward. A step_size of 1000 on energy means a 24.55 kWh session bills as 25 kWh. On a per-session basis that is trivial; across a network it is a material revenue difference, and across a roaming relationship it is a reconciliation gap if the two sides implement rounding differently.

When your computed total disagrees with a partner's CDR by a small amount, step_size is the first thing to check.

How tariffs reach the driver

Tariffs connect to infrastructure through tariff_ids on the Connector object in the Locations module. That is the only link, and it has consequences:

• Pricing is per connector, not per site. A location's AC and DC connectors will normally carry different tariffs.
• A connector can list several tariff IDs, in which case restrictions decide which applies. This is how a CPO offers a member rate and a walk-up rate at the same socket.
• A missing tariff_ids means you cannot show a price. Displaying “price unavailable” is correct; guessing is not.

OCPI 2.2.1 also supports type values including AD_HOC_PAYMENT, PROFILE_CHEAP, PROFILE_FAST and PROFILE_GREEN, which let a CPO publish alternative tariffs for smart-charging preferences.

Lessons from partner integrations

• Never cache a tariff without honouring last_updated. Price changes propagate through this field, and a stale cached tariff means quoting a price you cannot honour.
• Recompute and compare against every CDR. Independently calculating what you expected and diffing against the partner's figure catches tariff misinterpretation before customers do.
• Check element ordering during certification. A catch-all placed first is a common partner-side error and it silently flattens their own pricing.
• Show the driver the components, not just a rate. “22 INR/kWh, plus idle fee after 45 min” prevents the complaint that a headline rate cannot.
• Handle currency explicitly. Tariff currency is authoritative; never assume the driver's home currency.
• Expect a session to span multiple tariff elements. Any UI showing one price per session will misrepresent time-of-use tariffs.