# CCEE and ONS replace DESSEM version used to calculate Brazil’s spot price

> A model update followed an issue found in daily scheduling and marginal-price calculations; the new version took effect for calculations from 6 October.

- **Source date:** 2026-10-02
- **Original source:** [Câmara de Comercialização de Energia Elétrica (CCEE)](https://www.ccee.org.br/-/co-ccee-e-ons-atualizam-versao-do-modelo-dessem-para-calculo-do-preco-de-liquidacao-das-diferencas-pld-9)
- **Reading time:** 1 min
- **Language:** en
- **URL:** https://voltformer.com/news/ccee-ons-dessem-model-update-pld-october-2026
- **Markdown:** https://voltformer.com/news/ccee-ons-dessem-model-update-pld-october-2026.md

## A fast replacement of the operating model

CCEE and ONS announced on 2 October that DESSEM version 22.0.4 would be replaced by version 22.0.6. They said the need for an adjustment emerged during daily operation scheduling and calculation of the Settlement Price for Differences, Brazil’s short-term electricity price. Official use of the new version began on 5 October, affecting prices calculated from 6 October onward.

[Câmara de Comercialização de Energia Elétrica (CCEE)](https://www.ccee.org.br/-/co-ccee-e-ons-atualizam-versao-do-modelo-dessem-para-calculo-do-preco-de-liquidacao-das-diferencas-pld-9)

## The change addresses an infeasible case

The notice says version 22.0.4 did not properly handle a case in which the linear program used to calculate marginal operating cost was infeasible. Version 22.0.6 adds a fallback calculation using a mixed-integer model with commitment variables fixed. CCEE and ONS said the new version had been tested and validated by the sector’s permanent DESSEM group.

[Câmara de Comercialização de Energia Elétrica (CCEE)](https://www.ccee.org.br/-/co-ccee-e-ons-atualizam-versao-do-modelo-dessem-para-calculo-do-preco-de-liquidacao-das-diferencas-pld-9)

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