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This guide walks you through integrating Flex Lite into your EV charging platform. By the end, you’ll be able to send user charging schedules and receive optimized schedules that enable grid flexibility while maintaining user control.

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Before you begin…

Prefer to explore the API hands-on? Grab a focused OpenAPI spec or a ready-to-run Postman collection covering every endpoint in this flow, from eligibility through onboarding to rewards.

OpenAPI spec

OpenAPI 3.1 spec for the Flex Lite endpoints — import into your own tooling or hand to an LLM.

Postman collection

Pre-wired collection with auth set up — run Authenticate and the token is saved for every other request.

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Prerequisites

  • An Axle API token (see Authentication)
  • Basic site information (MPAN, address, postcode)
  • Ability to detect plug-in events
  • User’s desired charging schedule
  • Confirmed eligibility and user consent

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Step 1: Onboard your site and assets

Register the site and EV charger with Axle and enrol them in the limited_pause proposition — the proposition that lets Axle insert pauses into the user’s charging schedule.

Onboard

Create or update a site and its assets, and enrol them in a proposition.
If you want to enable payments for your users, include site.email in the onboard payload. A user email is required to process payments through our provider, Stripe. We also send payment-failure notifications and, if enabled, two-factor authentication codes to this address.

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Example

{
  "site": {
    "mpan": "1234567890123",
    "postcode": "SW1A 1AA",
    "street_address": "10 Downing Street",
    "email": "user@example.com",
    "gave_boundary_meter_consent_at": "2026-04-28T12:00:00Z"
  },
  "assets": [
    {
      "external_id": "charger-001",
      "type": "charger",
      "asset_model": "axle_charger_v1",
      "installation_date": "2026-03-26",
      "properties": {
        "power_kw": 7.4
      }
    }
  ],
  "proposition": "limited_pause"
}
Save site.site_id and each assets[].asset_id from the response — you’ll need the asset ID for sending schedules and the site ID for rewards and offboarding.You can also look up IDs later using each asset’s external_id.

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Step 2: Send plug-in event with charging schedule

When a user plugs in their EV, send their desired charging schedule to the plug-in-schedule endpoint. Axle will return a modified schedule optimized for grid flexibility.

Send plug-in schedule

Send a charging schedule and receive an optimised version

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Example

{
  "charging_schedule": [
    {
      "start_timestamp": "2025-06-27T22:00:00+00:00",
      "end_timestamp": "2025-06-28T06:00:00+00:00"
    }
  ]
}
Notice the response includes a 1-hour pause (01:00–02:00) — this is where the grid flexibility happens. The user earns rewards for this pause while still receiving the charging they need.

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Common questions

User actions always take precedence. If a user modifies their schedule or boosts charging after receiving the modified schedule from Axle, apply their requested changes and send Axle a new schedule.
Not every plug-in event will result in a modified schedule. Axle only adjusts schedules when there’s a grid flexibility opportunity that provides value. If no modification is beneficial, you’ll receive the original schedule back unchanged.
Axle’s optimization ensures the user receives sufficient energy based on their needs. The typical modification is a 30 minute pause, which maintains adequate charging for most use cases. If the original schedule is already tight, we may not modify it.

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Step 3: Stop participation (when needed)

There are two ways to stop a user’s participation. Pick based on what’s actually happening:
  • Unenrol when the user is opting out of Flex Lite specifically — for example, they leave the flex program in your app. The site and assets stay on the platform, any other propositions they’re enrolled in (such as Capacity Market) are unaffected, and they can re-enrol later and still access their payments.
  • Offboard when the user is leaving entirely — for example, they’ve moved house, or your support team is removing them. This unenrols from every proposition and deletes the site and its assets per data-retention policies. Payments can no longer be accessed afterwards, so prompt the user to withdraw any outstanding balance first.
If in doubt, use unenrol — it’s reversible.

Unenrol site

Stop this proposition without deleting the site

Offboard site and assets

Remove the site and its assets

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Next Steps

At this point, your users are onboarded and their schedules are being optimised. Now it’s time to set up revenue and payments.

Earning from EV Charging

Learn how to submit readings and manage user payments

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Further Reading

Advanced Onboarding

Need more control? Use initialise and enrol for a step-by-step onboarding flow.

Migrate to Smart Charging

Ready for more revenue? See what changes when upgrading to Smart Charging.