(Fortune) - A winery in Northern California’s Sonoma County was one of Tesla’s early battery customers. This is how the wine makers are using them.

Behind the La Crema Winery, in the wine-growing region of Sonoma County north of San Francisco, sit three white refrigerator-sized boxes that are an example of how the wine making here has gone high-tech. At least the winery’s use of energy has. This winery is a pioneer for what a certain electric car company run by Elon Musk hopes will become the norm for many others around the world.

Inside the white metal boxes sit thousands of Tesla batteries. While Tesla is better known for making luxury electric cars, it recently started selling batteries to businesses, utilities and home owners to help them save electricity and store solar energy.

At the winery the batteries store energy from the sun generated by solar panels on the winery’s rooftop. Tesla’s algorithms are also shifting the winery onto battery energy when electricity rates from the power grid are high, helping the wine makers save money on their energy bill.

Tesla is banking on turning its nascent battery push into a huge new business — one day it could even eclipse the company’s car sales. To succeed, Tesla will need to attract businesses like the winery as customers and convince them that batteries can save them money, make solar panels more efficient, and make the owners look cool.

This Tesla battery installation is just one of six that the Jackson family, which owns Jackson Family Wines has installed at their wineries around Northern California including Kendall-Jackson, their most well-known brand. The group was an early pilot customer for Tesla and started working with the electric car maker two years ago.

The batteries started operating in January of this year, several months before Tesla made its big announcement about its new battery products. Tesla is only selling these types of batteries in limited supply right now and the company says its sold out until mid-2016.

Below the scorching summer sun and 90-degree weather, the Tesla batteries rapidly charge and discharge energy at La Crema Winery, in Windsor, Calif. several times a minute, based on Tesla’s software and the power needs of the winery. The boxes routinely emit a clicking noise, which is the sound of the inverters converting the electricity from the batteries into usable energy.

The batteries at the wineries are among Tesla’s largest battery installations to date, and its first for a winery. There are 21 Tesla battery boxes, with 4.2 megawatts or 8.4 megawatt hours, of storage capacity, scattered across the six wineries.

For a company that traditionally makes Pinot Noirs, not electrons, that’s a whole lot of batteries. The Tesla batteries at the La Crema Winery alone are enough to power 18 Model S cars.

There are a handful of reasons why the Jackson family is using Tesla batteries at its wineries. On Thursday during a tour of the site, Julien Gervreau, Jackson Family Wine’s senior sustainability manager, explained to Fortune how the batteries work and how the winery has been trying to conserve energy and water.