# How accurate do our meters and scales have to be for CBAM, and what if one fails?

Canonical: https://senseible.earth/answers/cbam-measurement-uncertainty-targets-by-source-size

The Commission's guidance says the biggest sources, above 500,000 tonnes CO2 a year, should reach 1.5% uncertainty or better, while sources below 10,000 tonnes are acceptable at under 7.5%, if the cost is reasonable. A replacement instrument must be at least as accurate as the old one.

## The guide values

The aim is accuracy in proportion to size, with the lowest uncertainty on the biggest parts of your emissions.

- Source streams above 500,000 tonnes CO2 a year: uncertainty over the full reporting period of 1.5% or better.
- Source streams below 10,000 tonnes CO2 a year: uncertainty below 7.5% is considered acceptable.
- These apply if they do not lead to unreasonable costs.

## Replacing an instrument

If a meter fails, or calibration shows it no longer meets the uncertainty you claimed, replace it with one that meets the same or a better level. The guidance says to keep improving the monitoring method but never to fall below the existing standard.

## What to do now

1. Rank your source streams by tonnes of CO2 a year.
2. Check the stated uncertainty of the instrument on each large stream against the guide value.
3. Keep calibration certificates with the monitoring plan.
4. If you must swap a meter mid-year, tell your verifier and keep the data from both.

## What Senseible does here

Senseible reads your fuel, power and steam bills into verified emission records, so the monthly figures a monitoring plan needs are ready to hand to your verifier. Verified here means rule checks passed against the evidence. It is not third-party assurance, and a CBAM verifier still signs the report.

- [Does meter uncertainty count in CBAM materiality?](https://senseible.earth/answers/does-meter-uncertainty-count-in-cbam-materiality)
- [Meter failure and data gaps](https://senseible.earth/answers/cbam-meter-failure-data-gap-conservative-estimate)
- [CBAM Suite](https://senseible.earth/cbam-suite)

Sources: [European Commission, CBAM Guidance No. 3, calculation of embedded emissions](https://taxation-customs.ec.europa.eu/document/download/29b9eec7-1a4b-4eb6-ab85-96a0c9e35fd0_en?filename=Guidance%20No.%203%20-%20CBAM%20methods%20for%20the%20calculation%20of%20emissions%20embedded%20in%20goods.pdf)

Last reviewed 2026-11-04.