fuel mix

Fuel mix answers a deceptively simple question: of the megawatt-hours produced in a period, what share came from coal, gas, nuclear, wind, solar and the rest? Answering it well requires metered telemetry, not estimates - which is why grid operators are the primary source.

2 catalog records anchor the term. PJM appears in the catalog as '(LMP, Load, Fuel Mix, Reserves)' with tag 'fuel-mix', and its description covers 'metered and forecasted load, generation by fuel type, wind/solar output' - fuel mix delivered as an operations feed alongside prices and load. EIA's Electric Power Monthly reports 'generation by fuel, sector and state', adding the statistical layer: official monthly history sliced by owning sector and geography. Together they span the two granularities buyers need - real-time fleet behaviour and auditable national statistics.

Adjacent entries cover the components: net-generation for the volume base, wind-solar-output for the variable renewables, and capacity-factor for utilization.

Fuel-mix errors distort carbon and price conclusions simultaneously. Emissions intensity is computed as generation-weighted, so a mix that misclassifies one fuel's share shifts every tCO2/MWh figure downstream; and price formation analysis assumes the marginal fuel, which a coarse mix cannot reveal.

Three buyer consequences recur. Cadence mismatch: PJM's feed moves at operations timescales while the Electric Power Monthly is monthly - blending them without aligning periods creates phantom trends. Boundary mismatch: EIA slices by state, PJM by zone, so 'the same region' can mean different geographies in each source. Definition drift: 'generation by fuel' can mean net generation or metered output, and the sector split EIA provides (for example utility versus industrial) changes aggregates materially. Teams should fix source, period and boundary before computing any share, and prefer operator feeds for dispatch questions and EIA for official history.

1. Confirm the measurement basis. PJM publishes metered generation by fuel type as an operations feed; ask any vendor whether their 'fuel mix' is metered or modeled.

1. Align period before comparing sources. Operations-feed intervals and Electric Power Monthly months are different clocks - resample to a common period first.

1. Preserve the sector dimension. EIA's 'generation by fuel, sector and state' split lets you exclude non-utility segments; collapsing it changes the shares you report.

1. Track variable renewables separately. Wind and solar output is broken out in PJM's feed precisely because weather drives it - treat it as its own series, not a residual.

1. Validate against reserves context. PJM packages fuel mix with LMP, load and reserves; cross-checking mix shifts against price and load movements catches feed anomalies early.

Entries covering the quantities that compose the mix:

• capacity-factor
• net-generation
• wind-solar-output