Hourly AEF, MCTI Combined Margin, and net effective factor

Methodology comparison · Engie Brasil Energia

Three distinct quantities, each labelled for what it actually is. Karbera’s hourly AEF is the metered evidence layer computed from ONS dispatch. MCTI’s Combined Margin is the official displacement factor of record applied to every credited MWh. The net effective factor is credited tonnes ÷ gross verified generation — the Combined Margin multiplied by the operator’s beneficial-ownership share under Methodology v3.3, not a measured emission factor.

Annualized comparison — Engie Brasil Energia

CRIOS-v3.3 · grid-verified

The applied factor is MCTI’s national dispatch-analysis Combined Margin (0.3271 tCO₂/MWh, base year 2025). The hourly ONS-verified generation record — and the AEF derived from it — is the evidence beneath that factor, not a competing factor and never netted against it.

Karbera hourly AEF (annualized)
0.0356
tCO₂/MWh
Metered evidence layer — hourly ONS AEF × verified generation, gross
MCTI Combined Margin (applied factor)
0.3271
tCO₂/MWh
MCTI dispatch-analysis CM, base year 2025
AEF vs CM divergence
-89.1%
hourly AEF vs official CM
Two different quantities: average hourly grid intensity vs marginal displacement factor
Net effective factor (after ownership netting)
0.2283
tCO₂/MWh of gross generation
CM 0.3271 × beneficial-ownership share — not an emission-factor measurement
Ownership netting: -30.2% vs MCTI CM (implied beneficial-ownership share ≈ 69.8%).
Annual credited avoided emissions
14,936,119
tCO₂ (MCTI CM, ownership-netted)
Annual verified generation (gross)
65,419,042
MWh

Two separate quantities, shown separately — they are never compounded into one number. (1) AEF vs CM: Karbera’s hourly Average Emission Factor is the metered evidence layer derived from ONS dispatch; MCTI’s Combined Margin is the official marginal displacement factor applied to every credited MWh. They answer different questions — average hourly grid intensity versus what backs down at the margin — so the gap between them is definitional, not a discount. (2) Ownership netting: Methodology v3.3 credits each operator only its beneficial-ownership fraction of a jointly-held asset, so JV structures (Engie, Helexia) reduce credited tonnes proportionally. The net effective factor is simply CM × that share — an accounting artifact of who owns the asset, not a measurement of emissions.

Read the full Karbera methodology Why we use the government's factor