Understanding carbon equivalents

To provide a transparent breakdown of CO2e (Carbon Dioxide Equivalent) for a transaction, we offer equivalent scenarios to enhance users' comprehension of the figures.

For example, where the CO2e of a transaction is 5.2 kg, this could be presented as equivalent to driving a car for 31 km or charging your phone 630 times.

Equivalents are selected at random, but always on a fitting scale to be meaningful. This avoids overly-exaggerated comparisons (e.g. "charging 1,200,800 mobile phones") while keeping the experience varied, informative, and engaging.

Example calculations

Below are some of the calculations we use, with sources:

• 1 kg CO2e ≈ driving an average petrol car 6.1 km — UK Government conversion factors
• 1 kg CO2e ≈ charging 121 smartphones — EPA
• 1 kg CO2e ≈ recycling 0.043 trash bags of waste — EPA
• 1 kg CO2e ≈ switching 0.0379 normal bulbs to LEDs — EPA
• 1 kg CO2e ≈ CO2 absorbed by one tree over 36.5 days — One Tree Planted

Equivalent size buckets

Equivalents are bucketed based on the amount of CO2 so a reasonable comparison is always used:

Bucket	Range
Zero/unspecified	0 kg — "This transaction has low or unspecified emissions"
XSmall	0 – 0.5 kg
Small	0.5 – 10 kg
Medium	10 – 100 kg
Large	100 – 500 kg
XLarge	500 – 3,000 kg
XXLarge	3,000+ kg

Examples:

XSmall: "This is equivalent to the emissions from charging X smartphones."

XLarge: "This is equivalent to the emissions from flying a light private jet for X hours."

Implementation

Unspecified equivalents

The transaction API returns equivalents in two shapes within the transaction response object.

equivalents — an array of objects, each with a stable key, a numeric value, and a pre-rendered English text string. Use the key to localise the copy (see Localising the application).

{
  "equivalents": [
    {
      "key": "TRANS_BEL_M_35",
      "value": 0.8,
      "text": "This is equivalent to the emissions from air freighting 10 kg 0.8 times between Brussels and New York."
    }
  ]
}

You can display one or more of these to your users within your front end.

similar_to (deprecated) — an array of plain English strings, randomly selected, with no key for lookup. Prefer equivalents for new integrations.

{
  "similar_to": [
    "This is equivalent to the emissions from running a laptop for 18 hours.",
    "This is equivalent to the emissions from air freighting 10 kg 0.8 times between Geneva and New York.",
    "This is equivalent to the CO2 absorbed by planting and growing 20 trees for 10 years."
  ]
}

Specified equivalents

From insight endpoints, you can specify which equivalents to use. This is useful for creating your own copy and icons.

Request:

// e.g. on the /monthly-insights/breakdown endpoint
{
  "fixedEquivalents": ["car", "tree"]
}

Response:

{
  "equivalents": [
    {
      "key": "car",
      "value": 1000,
      "unit": "km",
      "text": "This is equivalent to the emissions from driving an average car 1000 km."
    },
    {
      "key": "tree",
      "value": 3000,
      "unit": "trees",
      "text": "This is equivalent to emissions absorbed by 3000 trees over 10 years."
    }
  ]
}