UK Carbon Intensity & Low-Carbon Windows

Get the half-hourly carbon intensity of electricity (gCO2/kWh) for Great Britain, its grid regions and UK postcodes from the Carbon Intensity API of the National Energy System Operator (NESO). Each half-hour has a forecast, an actual value (national only), an index and the generation mix. The Actor also finds the lowest-carbon time windows for EV charging, heat pumps, batch jobs and other flexible loads.

No login or API key is needed. The default run (Great Britain, London and Scotland for the next 24 hours) takes about 5 seconds, returns 153 rows (144 half-hours plus 9 ranked windows) and costs about $0.16 on the Free plan.

Table of contents

• What it does
• Quick start
• Use cases
• Input
• Output
• Pricing and limits
• API, export and integrations
• Troubleshooting
• FAQ
• Source and licence
• Support

What it does

The Actor reads the public Carbon Intensity API run by the National Energy System Operator (NESO). It does three things:

1. It gets every half-hour in your time range for each area you choose: Great Britain, any of the 17 NESO regions, and up to 5 postcodes.
2. It turns each half-hour into one clean row with UTC times, forecast and actual intensity, the index and the fuel mix.
3. It finds the best non-overlapping windows of the length you choose (for example 3 windows of 2 hours), ranked by the average forecast intensity.

Good fit

• You plan EV charging, heat pumps, batteries or batch jobs and need the greenest hours in the next day or two.
• You report on grid carbon intensity for a past day or week (ESG, energy dashboards).
• You compare regions or sites by postcode for the same time range.

Not a fit / limits

• It does not calculate the carbon footprint of your business and does not issue certificates or guarantees of origin.
• Great Britain only. Northern Ireland is not covered by the source.
• Regions and postcodes have forecasts only. The source has no regional actual values.
• Forecasts reach about 48 hours ahead. History starts in 2017–2018.

Quick start

1. Open the Input tab.
2. Keep the prefilled input: Great Britain, regions 13 (London) and 16 (Scotland), from now to +24h.
3. Optionally add a postcode such as M1 or EH1 1YZ.
4. Click Start.
5. In the Output tab, open Low-carbon windows only for the ranked windows, or All rows for every half-hour (the recordType column says period, window or area_status).

Expected result: one row per half-hour per area, plus the ranked windows for each area.

Use cases

Buyer job	Input path	Output entity	Key fields	Next integration
Schedule EV charging or a heat pump	postcodes, windowDurationHours, windowCount	window	from, to, averageForecastIntensity, windowRank	Your scheduler reads the rank 1 window
Daily ESG or energy report	startTime: "yesterday", includeNational	period	actualIntensity, forecastIntensity, generationMix	Export CSV/Excel or Google Sheets
Compare regions	regions	period	regionName, forecastIntensity, intensityIndex	Dashboard or BI tool

Input

Input fields

Field	Type	Default / prefill	Allowed values	Effect
includeNational	boolean	true	—	Great Britain series. This is the only series with actual values.
regions	array of strings	prefill ["13", "16"]	Region IDs "1"–"17" only	1–14 are distribution network regions (13 London, 1 North Scotland, …), 15 England, 16 Scotland, 17 Wales.
postcodes	array of strings	—	Up to 5 UK postcodes	Only the outward part is used and kept in the output (SW1A 1AA → SW1A).
startTime	string	now	now, today, yesterday, tomorrow, YYYY-MM-DD (a UK day), or an ISO date-time	ISO without an offset is read as UTC. The start is rounded down to the half-hour.
endTime	string	empty	+Nh, YYYY-MM-DD, or an ISO date-time	Empty = 24 hours after the start (or the end of the UK day for a day value). A date covers that whole UK day. Max range 7 days (168 hours).
includeHalfHourPeriods	boolean	true	—	Output one row per half-hour.
includeGenerationMix	boolean	true	—	Add the fuel mix to each half-hour (national and regional).
findLowCarbonWindows	boolean	true	—	Output ranked window rows.
windowDurationHours	number	2	0.5–24, in steps of 0.5	Length of each window. It must fit inside the range.
windowCount	integer	3	1–10	Windows per area. Fewer are returned if the range is too short.
windowsFromNowOnly	boolean	true	—	Only search windows from the current half-hour onward. Turn it off to rank windows in a past range.

At least one area is required. Duplicate regions and postcodes with the same outward code are merged. If both includeHalfHourPeriods and findLowCarbonWindows are off, the input is rejected.

Interacting settings

When	Effective behavior
startTime is a day and endTime is empty	The range is that whole UK calendar day: 48 half-hours, or 46/50 on clock-change days.
The range is in the past and windowsFromNowOnly is true	No windows are found. Set windowsFromNowOnly to false.
A window has already started	It can still be ranked; its isUpcoming is false.

Input example

{
  "includeNational": true,
  "regions": ["13", "16"],
  "postcodes": ["M1 1AE"],
  "startTime": "now",
  "endTime": "+24h",
  "includeGenerationMix": true,
  "findLowCarbonWindows": true,
  "windowDurationHours": 2,
  "windowCount": 3
}

Expected output: 4 areas × 48 half-hours = 192 period rows plus up to 12 window rows. M1 1AE is reported as M1.

Output

Each Dataset row has a recordType:

• period: one half-hour of one area;
• window: one ranked low-carbon window of one area;
• area_status: an area with no rows (not_found, no_data or error). These rows are free.

Output fields

Field	Meaning	Can be empty?
recordType	period, window or area_status	no
area, areaType	Area label and type (national, region, postcode)	no
regionId, regionName, dnoRegion	NESO region; regionId is null for Great Britain	yes
postcode	Outward postcode of the lookup	yes
from, to	Start and end, UTC ISO 8601	null on status rows
forecastIntensity	Forecast, gCO2/kWh	yes
actualIntensity	Actual, gCO2/kWh. National past half-hours only; otherwise null (not 0)	yes
intensityIndex	very low, low, moderate, high, very high	yes
unit	Always gCO2/kWh	no
generationMix	Percent by fuel: biomass, coal, gas, imports, nuclear, hydro, solar, wind, other	yes
windowRank	1 = lowest average forecast	window rows only
windowDurationHours, averageForecastIntensity, minForecastIntensity, maxForecastIntensity	Window length and its forecast (average rounded to 0.1)	window rows only
isUpcoming	true if the window starts after the run started	window rows only
status, message	ok, or the reason for a status row	message yes
provider, sourceUrl, fetchedAt	Source, exact API request and fetch time (UTC)	no

The key-value store record WINDOWS holds only the window rows (a JSON array). The record RUN_SUMMARY has the run status, counts per area, the best windows, request statistics, warnings and the attribution text.

The Dataset has two table views, Overview and Fuel mix. Both show all rows; filter by recordType if you need one kind. To get only windows in the Dataset, turn off includeHalfHourPeriods.

Output example

A real row from the default run on 2026-10-12, trimmed:

{
  "recordType": "period",
  "area": "GB (national)",
  "areaType": "national",
  "from": "2026-10-12T13:30:00Z",
  "to": "2026-10-12T14:00:00Z",
  "forecastIntensity": 73,
  "actualIntensity": null,
  "intensityIndex": "low",
  "unit": "gCO2/kWh",
  "generationMix": { "wind": 49.5, "gas": 13, "nuclear": 11.5, "imports": 10.7, "biomass": 8.7, "solar": 6.6, "hydro": 0, "coal": 0, "other": 0 },
  "status": "ok",
  "provider": "Carbon Intensity API (National Energy System Operator)",
  "sourceUrl": "https://api.carbonintensity.org.uk/intensity/2026-10-12T13:30Z/2026-10-13T13:30Z",
  "fetchedAt": "2026-10-12T13:52:42Z"
}

And a window row from the same run:

{
  "recordType": "window",
  "area": "GB (national)",
  "from": "2026-10-13T11:30:00Z",
  "to": "2026-10-13T13:30:00Z",
  "windowRank": 1,
  "windowDurationHours": 2,
  "averageForecastIntensity": 36.5,
  "minForecastIntensity": 35,
  "maxForecastIntensity": 38,
  "isUpcoming": true
}

Output surfaces

Situation	What you get	What to do
Normal run	period and window rows, run status COMPLETE	Use the Overview view or the WINDOWS record
Unknown postcode	One area_status row with not_found	Check the postcode; Northern Ireland is not covered
Range with no data (too far ahead or before 2017)	area_status row with no_data, run status NO_RESULTS	Choose a range within the next ~48 hours or the past
Some areas failed	Rows for the others, run status PARTIAL	Read RUN_SUMMARY.areas and retry later
Invalid input	Run fails with a clear message, no rows	Fix the field named in the message

Pricing and limits

Pricing unit

This Actor uses pay-per-event pricing:

Event	Price
Actor start (one per run at the default 256 MB memory)	$0.005
Result row (one period or window row)	$0.001 (Free plan), $0.00095 (Bronze), $0.0009 (Silver), $0.00085 (Gold and higher)

area_status rows are free. A run with no data (for example a range too far ahead) costs only the start event. If the source fails, no rows are charged. Platform usage is included in the price.

Cost examples (Free plan prices)

Scenario	Input scope	Rows	Cost
Default run	GB + 2 regions, 24 h, 3 windows each	153	$0.158
One window only	1 postcode, periods off, 1 window	1	$0.006
Two days, six areas	GB + 5 regions, 48 h, 3 windows each	594	$0.599
Largest tested	GB + 17 regions + 5 postcodes, 7 days, windows on	7,958	$7.96

The largest tested run finished in 41 seconds. You can set a maximum total charge for a run; the Actor stops saving rows when it is reached (run status CAPPED).

API, export and integrations

• API: start the Actor with the Apify API and read the Dataset items, or the WINDOWS key-value record for the ranked windows only.
• Export: download the Dataset as JSON, CSV, Excel, XML or HTML.
• Scheduling: run it every day (for example at 18:00 UK time) with Apify schedules to plan the next day's flexible loads.
• Webhooks / no-code: send results to Make, Zapier, Google Sheets or your own webhook with Apify integrations.

Use with AI agents (MCP)

• MCP server URL with only this Actor: https://mcp.apify.com?tools=cliqtomedia/uk-carbon-intensity.

• Smallest useful input:

  { "includeNational": true, "startTime": "now", "endTime": "+24h", "includeHalfHourPeriods": false, "windowCount": 3 }
  

• Key output fields: from, to, averageForecastIntensity, windowRank on window rows; forecastIntensity, intensityIndex on period rows.

• A typical call takes about 5 seconds and costs $0.008 for 3 window rows. Limits: 7 days per run, up to 5 postcodes, region IDs "1"–"17".

Troubleshooting

Input is rejected for a region name

Symptom: the run does not start and says the region value is not allowed. Reason: the input form accepts region IDs only. Action: use "13" for London, "16" for Scotland, and so on (see the Input table).

No windows in the output

Symptom: period rows exist, but there are no window rows. Reason: the range is in the past and windowsFromNowOnly is true, or the range is shorter than windowDurationHours. Action: set windowsFromNowOnly to false for past ranges, or make the window shorter.

Scotland shows 0 gCO2/kWh

Symptom: many half-hours for Scotland (16), North Scotland (1) or Scottish postcodes have forecast 0, and several windows have an average of 0. Reason: this is the value the source publishes for these areas. The Actor keeps it as is and does not invent a ranking. When every forecast in the range is the same, RUN_SUMMARY.warnings says that the windows are ties ordered by start time. Action: none needed; use another region if you need a ranking.

A postcode returns not_found

Symptom: one area_status row with not_found. Reason: the source does not know this outward postcode, or it is in Northern Ireland. Action: check the postcode. Other areas in the same run are not affected.

FAQ

Do I need an account or API key for the source?

No. The source is a free public API. You only need an Apify account to run the Actor.

Why is actualIntensity null?

The source publishes actual values only for Great Britain as a whole and only for half-hours that have passed. Regions and postcodes have forecasts only. A null means "no value", never 0.

How fresh is the data?

Each run requests the source live. fetchedAt shows when. Forecasts change during the day, so a later run can show different forecasts for the same half-hour.

Why are times in UTC?

The source uses UTC. A UK calendar day (today, 2026-10-25) is converted for you, so clock-change days have 46 or 50 half-hours.

Source and licence

Contains data from the Carbon Intensity API by National Energy System Operator, licensed under CC BY 4.0. The Actor reformats it (UTC periods, window ranking). This Actor is not affiliated with or endorsed by NESO. Every row keeps provider, sourceUrl and fetchedAt.

Support

For bugs, questions or feature requests, open an issue on the Actor's Issues tab in Apify Store. Include the run ID and your input. Do not send API tokens or other secrets.