The U.S. grid moves roughly — TWh/year — the largest meshed
electrical machine on earth. Natural gas is the plurality source today; nuclear
is the second-largest carbon-free contributor; wind and solar combined have
overtaken coal. The grid itself doesn't store energy — generation has to match demand
second-by-second across three asynchronous interconnections (Eastern, Western, ERCOT).
Color identifies each fuel; bar length is generation share.
Natural gasNuclearCoalWindSolarHydroBiomass / other
Total generation
—
TWh/year · all sources
—
Carbon-free share
—
nuclear + hydro + wind + solar
Wind + solar combined
—
— of total
Carbon intensity
—
g CO₂/kWh · vs ~570 in 2005
SOURCE · U.S. Energy Information Administration, Electric Power Monthly (Table 1.1,
net generation by energy source). Annual totals shown trailing twelve months. Demand
breakdown from EPM Table 5.1; transmission losses estimated at ~5% of net generation,
consistent with EIA's State Electricity Profiles. Carbon intensity is a weighted average
of source-level emission factors (gas ~400 g/kWh, coal ~900, oil ~700, others ~0)
against the live generation mix. EIA hourly data is also available via the EIA-930
operational dataset for future drill-downs.