Usage Screen: Handling tariffs with different standing charge, (and over time)

[ryanw-mobile]

Example: E-1R-VAR-22-11-01-A

• Even for the current standing charge, we have to pick the right payment method.
• We also have to decide if we want to fit past standing charges - the calculation will be inefficient without a DB to cache the data.

  "count": 8,
  "next": null,
  "previous": null,
  "results": [
    {
      "value_exc_vat": 45.57,
      "value_inc_vat": 47.8485,
      "valid_from": "2024-03-31T23:00:00Z",
      "valid_to": null,
      "payment_method": "DIRECT_DEBIT"
    },
    {
      "value_exc_vat": 50.79,
      "value_inc_vat": 53.3295,
      "valid_from": "2024-03-31T23:00:00Z",
      "valid_to": null,
      "payment_method": "NON_DIRECT_DEBIT"
    },
    {
      "value_exc_vat": 40.01,
      "value_inc_vat": 42.0105,
      "valid_from": "2024-01-01T00:00:00Z",
      "valid_to": "2024-03-31T23:00:00Z",
      "payment_method": "DIRECT_DEBIT"
    },
    {
      "value_exc_vat": 45.23,
      "value_inc_vat": 47.4915,
      "valid_from": "2024-01-01T00:00:00Z",
      "valid_to": "2024-03-31T23:00:00Z",
      "payment_method": "NON_DIRECT_DEBIT"
    },
    {
      "value_exc_vat": 40.0125,
      "value_inc_vat": 42.013125,
      "valid_from": "2023-03-31T23:00:00Z",
      "valid_to": "2024-01-01T00:00:00Z",
      "payment_method": "DIRECT_DEBIT"
    },
    {
      "value_exc_vat": 45.2311,
      "value_inc_vat": 47.492655,
      "valid_from": "2023-03-31T23:00:00Z",
      "valid_to": "2024-01-01T00:00:00Z",
      "payment_method": "NON_DIRECT_DEBIT"
    },
    {
      "value_exc_vat": 35.5166,
      "value_inc_vat": 37.29243,
      "valid_from": "2022-11-01T00:00:00Z",
      "valid_to": "2023-03-31T23:00:00Z",
      "payment_method": "DIRECT_DEBIT"
    },
    {
      "value_exc_vat": 40.6283,
      "value_inc_vat": 42.659715,
      "valid_from": "2022-11-01T00:00:00Z",
      "valid_to": "2023-03-31T23:00:00Z",
      "payment_method": "NON_DIRECT_DEBIT"
    }
  ]
}```

[ryanw-mobile]

This can be the final missing piece that blocks us from confidently circulating this app - the billing section we have to provide a real cost calculation under all filters.
Right now we can only get this accurate in half-hourly view.