Tesla's Gigafactory, the world's largest lithium-ion battery factory, is expected to generate as much renewable energy as it needs to operate -- and then some.

Last week, Tesla announced it would build its factory outside of Reno, Nevada.

Using conservative estimates, the Gigafactoy's trifecta of renewable energy sources could generate more than 2,900MWh of renewable electricity daily, which amounts to 20% more than it needs, according to Tom Lombardo, a professor of engineering and technology at Rock Valley College in Rockford, Ill.

"These are conservative estimates on production and worst-case estimates on consumption, and it's clear that there's enough renewable energy to run the plant with some to spare," Lombardo wrote in wrote in a recent blog.

The factory, preparation for which has already begun at the Reno Tahoe Industrial Center, will be shaped like a diamond. The diamond shape, according to Tesla CEO Elon Musk, better fits the contour of the surrounding environment so that less dirt has to be removed to build it.

The factory is also aligned on true north so that solar panels on its roof are exposed to the maximum amount of sunlight possible, Musk said.

"This factory will produce its own energy as well. Through a combination of geothermal, wind and solar it will produce all the energy it needs," Musk said. "So it'll be sort of a self-contained factory."

Renewable ROI

More than half of Fortune 100 companies collectively saved more than $1.1B annually by reducing carbon emissions and rolling out renewable energy projects over the past year, according to a recent report titled "Power Forward 2.0." Collectively, 43% of Fortune 500 companies, or 215 in all, have also set targets in one of three categories: greenhouse gas reduction, energy efficiency and renewable energy. When narrowed to just the Fortune 100, 60% of the companies have set the same clean energy goals.

As admirable as it is for Tesla's battery factory to run 100% on renewable energy, it's currently not a viable option for most companies mainly because of the variability of renewable energy.

Tesla's 10 million square foot factory will be covered in solar panels, and be plugged into a nearby wind turbine farm and geothermal electricity plant, according to Tesla CEO Elon Musk.

A battery factory of that size is estimated to consume 100 megawatts (MW) of power at peak capacity or 2,400MWh per day, according to Navigant Research. By comparison, that's the equivalent electricity consumption of about 80,000 homes.

"It's an enormous amount of energy for a single facility," said Sam Jaffe, a principal research analyst with Navigant.

Most of the energy required by the Gigafactory, Jaffe said, will be used to power ovens, which are used to bake chemical powders onto metal foil used in the production of cathodes and anodes -- the positive and negative points of a battery.

Tesla's choice of sites for its Gigafactory was optimal for several reasons that wouldn't necessarily benefit other types of factories. First, Reno is also one of the few areas in the world where the Earth's crust is thin enough to offer access to geothermal energy, i.e. heat from the Earth's mantle.

That geothermal heat is not variable, but constant, and can be used in the Gigafactory's ovens or to create steam to power turbines.

While Reno is an arid region, precluding manufacturing that requires a lot of water, it does get on average five peak hours of sun per day compared to other areas of the country, such as the Northeast, which get about 2 hours.

"It's the predictability that is so much better in that geography," Gaffe said.

The other top energy use in the Gigafactory will be to fully charge up batteries and then discharge them in order to condition them for use. However, in an efficient battery factory, discharging batteries can be used to charge others - to power requirements should be minimal, Jaffe said.

Lastly, the Gigafactory is producing batteries, which Tesla could then use to cheaply store power during off-peak renewable energy production.

Not really "off grid"

Lombardo doesn't believe the factory, however, will be energy independent based on its own renewable power plants. Instead, it will use "net metering", a method whereby Tesla will generate its own electricity and sell excess back to utilities. Then, during times when Tesla's own renewable energy production falls below demand, the electrical grid will intelligently route to it electricity based on energy credits.

"It's more reliable, more cost-effective, and location-independent," Lombardo said in an email reply to Computerworld. "Even Tesla isn't necessarily going off-grid. Musk said "net-zero energy," which just means that they'll generate as much energy as they use."

On average, Reno basks in five peak hours of sunlight per day.

Using an average 20% efficiency for rooftop photovoltaic (PV) panels, the Gigafactory's 10 million square foot roof would produce 850MWh of solar power daily, Lombardo said.

Additionally, using Tesla's own artist's rendition of the Gigafacotry, Lombardo estimates that the Gigafactory would have 85 wind turbines able to generate about 1,836 MWh of power daily.

"Reno is no stranger to geothermal energy - it has several plants in operation already. The newest has a 20MW capacity," Lombardo wrote in his blog. "Let's say Tesla goes small and builds one with only half of that capacity. That 10MW plant would produce 240MWh of daily geothermal electricity.

Through economies of scale, Tesla's Gigafactory is expected to drive down the per-kilowatt cost of the company's own lithium-ion car batteries by more than 30% in 2017, the first year of production.

By 2020, Tesla believes its Gigafactory will produce more lithium-ion batteries in one year than were produced worldwide in 2013.

During a press conference outside of the Nevada state capital building last week, Gov. Brian Sandoval said the Gigafactory will have a nearly $100 billion in economic impact to Nevada over the next 20 years," Sandoval said.

"It's not just going to be the biggest lithium-ion battery factory in the world, but it will actually be bigger than the sum of all lithium-ion battery factories in the world," Musk said. "It's a heck of a big factory."