Table 1.

Changes in renewable curtailment and CO₂ emissions resulting from lower Li-ion and PSB costs and higher NaS costs as a percentage of renewable curtailment and CO₂-emissions levels with the baseline costs

Technology	Renewable Curtailment (%)		CO2 Emissions (%)
	CAISO	ERCOT	CAISO	ERCOT
Li-ion	−27.1	−56.9	−22.3	−1.6
NaS	60.2	89.6	43.9	1.4
PSB	−15.1	−34.4	−8.9	−0.5

Results shown are for 2012 assuming 20-GW wind- and 40-GW solar-penetration level, a $200 per ton CO₂-emissions tax, and base-case minimum-dispatchability requirements of the CAISO and ERCOT systems