Chapter 5 · the fuel mix

What's on the wire

The fuel mix on each grid varies hour by hour. In which markets does solar push gas off at noon, and in which does coal run flat through the day? Each ring below is 24 hours of an average day on one major balancing authority, from EIA-930.

Clock

24-hour fuel-mix clock
Each ring band is a fuel; ring height encodes mean MWh generated at that hour of the day. Annual mode averages every hour over the full year; seasonal modes use only the months in that season.

Generation + demand, hour by hour

Stacked area is generation by fuel (same numbers as the clock). The dark line is mean grid demand at that hour — when generation falls below demand the BA imports; above it, exports.

Stacked area: hourly fuel mix with demand overlay

Carbon-aware siting · 100 MW always-on

A constant 100 MW load on this grid would draw the following fuel mix, weighted by what's generating at each hour.

FuelShareMW (avg)
Caveat. EIA-930 reports generation at the BA level, not at the meter. The carbon-aware panel is a first-order estimate of what would back-fill a constant load on each BA — it does not model interchange between BAs, so a CAISO load that's actually served by Northwest hydro imports looks "all CAISO" here. Full methodology & sources.
What this doesn't show
  • Interchange between BAs isn't modeled. Loads served by imports look like they're on the importing BA's mix.
  • Timezone is fixed (no DST). The hour-of-day curve smears by an hour at the DST boundary. Acceptable for a screening signal.
  • The data is a full-year mean from EIA-930. For real-time data, see gridstatus.io.