Hawai‘i was the first state to set a goal of 100 percent renewable energy by 2045. It handily beat its first progress goal of 30 percent by 2020, hitting almost 35 percent. The island of Kauai surpassed its 2020 target of 50 percent renewables by achieving 60 percent. Hawai‘i is an important case study because after setting a timeline to decarbonize its power, it is finding it can move faster than initially expected. The same law targeting 100 percent clean energy also specified ending coal use by 2023.
The economics are favorable for solar in Hawai‘i because coal, fuel oil, and diesel all must be imported and thus are expensive. The cost-effectiveness of solar has led to half of Hawai‘i’s renewable energy coming from rooftop solar. In second place is wind power, and large-scale solar holds third place. The early proliferation of distributed (rooftop) solar has forced the adoption of batteries to handle the surplus, shifting the excess to valuable evening hours. Today, 78 percent of new home solar installations include batteries.
Hawai‘i’s last coal-fired power plant, located on Oahu, will shut down next year. This plant has provided much of the flexibility for meeting peak demand power. State energy planners have chosen to replace it with even more solar, large- and small-scale, as well as to incentivize homeowners who have solar and batteries to share a proportion of their power to help the grid during peak hours. With incentives of up to $4,250, it is expected that this program will supply 30 percent of the power that the coal plant provides. In addition, they are building a big battery consisting of 158 Tesla Megapacks. It will be one of the largest stand-alone batteries in the world. Since it will not have on-site solar, it will charge from the grid, creating flexibility on a scale that has never been done before.