Oh sorry, I misread. They expect prices to fall 27%, but renewables are at about 40% penetration (on Big Island).
But if I'm not mistaken again, this 40% doesn't include about 10% of distributed solar PV (according to the first chart in the article).
This 10% of PV is interesting because it shows that you can introduce 10% of PV without significant amounts of storage. Italy, which has second highest PV penetration, is at 7%.