Hawaii is on a mission to be powered 100 percent by renewable energy by 2045. For this remote group of islands, achieving a fully renewable electricity system also means dramatically reducing the state's dependence on oil. 

Reaching the 100 percent renewable energy target "requires us to rethink everything we do," according to the Hawaiian Electric Companies -- Hawaiian Electric, Maui Electric and Hawaii Electric Light -- which provide electricity for 95 percent of Hawaii residents on the islands of Oahu, Maui, Molokai, Lanai and Hawaii Island.

To mark Earth Day on April 22, the Hawaiian Electric Companies published several stats touting the utilities' clean energy progress. Here are the highlights.

More renewables in the mix

Hawaiian Electric Companies reached a new milestone in 2016, with 26 percent of the electricity used by customers coming from renewable resources -- up from 23 percent the year before. On the island of Hawaii, renewable electricity use surpassed the halfway mark for the first time, reaching 54 percent, up from 49 percent in 2015. Maui reached a record high of 37 percent last year, and 19 percent of electricity used by customers came from renewable resources on Oahu.

When it comes to the types of renewable resources in the companies' energy mix, customer-owned solar dominates with 34 percent of renewable energy generated last year, followed by wind at 29 percent and biomass in third at 19 percent. 

Each utility detailed its clean energy goals in the Power Supply Improvement Plan submitted to the Hawaiian Public Utilities Commission in December 2016. The goals include tripling distributed solar (of all project sizes) by 2030, and providing customers with more energy options, including community solar, demand response and electric vehicle programs. 

While Hawaiian utilities expect to see even greater amounts of distributed solar deployed in the years to come, high levels of residential solar generation have already created problems for Hawaii's grid. In late 2015, the PUC replaced retail-rate net metering with "grid-supply" and "self-supply" tariffs in order to moderate rooftop solar growth. Shortly after the limited grid-supply program reached its cap, Hawaii's residential solar market crashed

Earlier this month, however, regulators reopened the grid-supply program by removing projects from the queue that had been approved but never completed. Estimates show around 20 megawatts of grid-supply capacity is now available for customers of the three companies, representing about 2,800 private rooftop solar systems. The Hawaiian Electric Companies report hundreds of applications are already in line for processing, and will be processed in the order in which they were received and only as capacity becomes available through October 21, 2017.

Looking further ahead, the Power Supply Improvement Plan forecasts Hawaiian Electric Companies will exceed the state’s mandated renewable energy milestones, with 48 percent renewable energy by the end of 2020; 72 percent by the end of 2030; and 100 percent by the end of 2040 -- five years ahead of the 2045 deadline.

Oil consumption down 21 percent

Electricity generation and oil consumption go hand in hand on the Hawaiian islands. So as renewable energy consumption has increased, Hawaiian Electric Companies have been able to back oil out of the system.

From 2008 to 2016, all three companies collectively cut their oil use in generators from 10.7 million barrels to 8.5 million barrels -- a 21 percent decrease. On Oahu, where energy demands are the greatest, Hawaiian Electric's oil use fell from 7.8 million barrels to 6 million barrels. 

The utilities' goal is to reduce greenhouse gas emissions to 2010 levels by 2020 -- a target they're already on track to surpass. To do that, the Hawaiian Electric Companies are expected to cut emissions by 865,000 tons each year, which is equivalent to the energy consumed by 116,000 homes per year, or cutting 1.8 million barrels of oil per year.

Electric-vehicle use accelerates

In Hawaiian Electric Companies territory, the number of registered plug-in electric vehicles (EV) has broken the 5,000 mark. That milestone ranks Hawaii second in the nation for EV adoption per capita, after California.

The companies report a dozen fast chargers are now available at shopping centers, visitor attractions and on utility property across the five islands served, and more are coming. "Transactions at our companies’ fast chargers shot up in March as EVs on the road increased and drivers became more aware of the growing number of fast chargers," according to a press release. 

Hawaiian utilities have partnered with branches of government, nonprofits and private companies to accelerate the adoption of EVs. Most recently, the Hawaiian Electric Companies collaborated with Nissan to offer a $10,000 rebate for the new Leaf sedan.