Serveral US states, like Washington, are passing laws to target 100% clean energy. Hawaii and others are aiming for 100% renewables. With the renewable energy transition now being driven by economics as well as policy, low-cost storage is the key to supporting the intermittency of wind and solar. Jessika Trancik’s MIT lab explored just how cheap storage would need to be to support 100% renewables. The answer… $20k per kWh in energy capacity.

From the study, published in the journal, Joule…

“Deeply decarbonizing electricity production will likely require that low-carbon sources meet energy demand throughout days, years, and decades. Wind and solar energy are possible low-carbon options, but resource variability can limit their reliability. Storage can help address this challenge by shaping intermittent resources into desired output profiles. But can solar and wind energy with storage cost-competitively fulfill this role? How do diverse storage technologies compare? We address these questions by analyzing systems that combine wind and solar energy with storage to meet various demand profiles. We estimate that energy storage capacity costs below a roughly $20/kWh target would allow a wind-solar mix to provide cost-competitive baseload electricity in resource-abundant locations such as Texas and Arizona. Relaxing reliability constraints by allowing for a few percent of downtime hours raises storage cost targets considerably, but would require supplemental technologies. Finally, we discuss storage technologies that could reach the estimated cost targets.”

Sources and additional reading

Getting to 100% renewables requires cheap energy storage. But how cheap? (Excellent summary by David Roberts, Vox)
Storage Requirements and Costs of Shaping Renewable Energy Toward Grid Decarbonization (Original publication in Joule)