On the sleepy Hawaiian island of Kauai sits a first of its kind solar and battery project.

The rain pauses, the clouds part, and the sun finally shines down on a sprawling 65-acre solar panel farm, surrounded by bright green grass and tropical foliage, on the plush Hawaiian island of Kauai.

The close to 55,000 solar panels, which are still being installed on the site, aren’t yet converting the sun’s light into electricity, but something else quite remarkable is happening at the project on this Wednesday morning in mid-November. Bay Area-based solar company SolarCity, which is in the process of being acquired by energy company Tesla, is installing the first of a series of batteries provided by Tesla in a section of the solar site.

When the project is finished early next year, the batteries will store the sun’s energy during the day to be used at night, when the local utility, Kauai Island Utility Cooperative, usually starts turning on fossil fuel-consuming generators. When the farm is switched on it will be one of the first ones where a utility is using big blocks of Tesla batteries, and it will also be one of the first utility systems to use solar and batteries to displace power-hungry generators.

While the island’s population is relatively small (the utility has just 33,000 members) the solar and battery project is a glimpse into a future in which energy companies combine clean power with energy storage in order to lower greenhouse gas emissions, and in some cases reduce energy costs. In addition, the project shows how Tesla TSLA -0.29% , an electric car and battery tech maker, could work closely with SolarCity SCTY 0.25% to construct the solar and battery vision laid out by billionaire Elon Musk, the CEO of Tesla and Chairman of both companies.

The companies will hold a shareholder vote on Thursday afternoon, which will determine if the two firms will merge into one. A day before the crucial meeting, SolarCity and utility Kauai Island Utility Cooperative (KIUC) showed Fortune around the project, a first by a media entity.

Energy Tech In Paradise

On Wednesday morning, a handful of the 60 plus workers on the site drill into paved rectangles where the first of Tesla’s so-called battery “Powerpacks” will soon be installed. The boxy white battery containers—which are covered by “Tesla Energy”-branded tarps and were shipped to the island via boat—contain rows of lithium-ion batteries that were assembled at Tesla’s massive battery factory, itself under construction outside of Reno, Nev.

Last year, Tesla officially announced that it would sell batteries for the power grid, buildings, and homes after building a business on battery-powered electric cars. However, for many years before that Tesla and SolarCity worked together testing how solar panels and batteries could be used for customers with intensive or unique energy needs.

Since SolarCity’s deal with the Kauai utility last year, workers have been installing steel posts into the ground and mounting silicon-based solar panels that face the sun. The crew then string wiring along the rows of panels, connecting the rectangular electricity generators to inverters that convert the solar energy into usable electricity. The site is about 50% finished, says SolarCity’s senior commercial project manager, Danny Valdez.

For KIUC, the project isn’t just about solar; the utility already has that in spades. The issue is, KIUC can’t add any more solar panels to the island without adding more energy storage, says KIUC engineering manager John Cox. It has so much solar that on some sunny, cloudless days, it’s getting a peak energy load of 90% from renewables—and sometimes 70% from solar alone.

To take the next step, KIUC needed technology that could store the energy for when fast-moving clouds cover the solar panels or when night falls. The island sees peak energy demand start around 8 p.m., as residents return home and turn on lights and appliances.

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