Elon Musk is defending Tesla's acquisition of SolarCity against angry shareholders. This is the story of how it was transformed into Tesla Energy.

Musk's cousins founded SolarCity at his suggestion, and Musk injected $10 million into the project himself.

The company initially enjoyed success, and in 2013 became the top residential installer for solar panels in the US, according to solar panel comparison site Energy Sage.

Its stock peaked in February 2014 at $88.35 a share — but then it began to go downhill.

In October 2015, a quarter of SolarCity's value got wiped out, meaning it lost its "unicorn" status (a unicorn is a company valued at more than $1 billion).

The sudden drop in its value came after Lyndon Rive said the company would have to focus on cutting costs, as its rapid growth meant it had sunk a lot of money into infrastructure that wouldn't make it any cash in the near future.

"The downside of growing at 80% or 90% is you have to make investments into the infrastructure today, but you only recognize the benefit of that investment two quarters to three quarters later," Rive said.

Documents obtained by shareholder lawsuits revealed executives thought the company was facing a cash crisis as early as September 2015.

SolarCity said in an official blog post on August 1, 2016, that Tesla had made an all-stock offer on June 21.

"Now is the right time to bring our two companies together: Tesla is getting ready to scale our Powerwall and Powerpack stationary storage products and SolarCity is getting ready to offer next-generation differentiated solar solutions," SolarCity's blog said.

The deal was approved by Tesla's shareholders in November 2016. At the time of the acquisition, Elon Musk owned a 22% stake in SolarCity.

Lyndon Rive announced in May 2017 he would be leaving Tesla in June.

He told employees in a letter he was an "entrepreneur at heart," and wanted to leave to build a new startup. Rive told Reuters at the time SolarCity was "healthier than it's ever been."

Peter Rive, Lyndon's co-founder and CTO, left the company in July 2017. In an internal letter published by Green Tech Media, Rive said he had decided to "take a break and focus on some other projects."

"I plan to spend more time exploring the outdoors, more time with my family, and helping non-profit solar projects in the developing world," Rive added.

While Tesla Energy has continued to sell the traditional solar panels SolarCity used to install — which are made by third-party manufacturers such as Trina Solar — it has brought two new products to market since the acquisition.

The first was its Powerwall storage battery, designed to store energy generated by a customer's solar system so even if the power goes down in their neighbourhood they'll have access to power.

It's not entirely clear whether development on the Powerwall began before or after the acquisition. Tesla gave a preview of the storage battery at an event in May 2015, but in testimony on Tuesday Musk said development of the Powerwall was "beginning" when the acquisition happened in 2016.

"We were beginning development of the Tesla Powerwall battery. And in order to have a compelling product, you really needed to have a tightly integrated solar and battery solution. And we could not create a well-integrated product if SolarCity was a separate company," Musk told the court.

The second is the Solar Roof, which instead of bolting panels on top of a customer's roof replaces the entire roof with photovoltaic shingles.

Musk debuted the Solar Roof in October 2016 during a glitzy event on a house from the show "Desperate Housewives."

"It needs to be beautiful, affordable and seamlessly integrated," Musk said at the unveiling event, adding: "You'll want to call your neighbors over and say, 'check out this sweet roof.'"

Depositions from Tesla executives later revealed the tiles Musk had shown off at the event hadn't been operational.

Tesla did not start actually installing Solar Roof until 2019. In a deposition, Musk said this was because Tesla had to divert resources away from Tesla Energy to focus on the Model 3 production ramp.

Elon Musk announced the policy change via a tweet. "Solar power will feed exclusively to Powerwall. Powerwall will interface only between utility meter & house main breaker panel, enabling super simple install & seamless whole house backup during utility dropouts," Musk said.

The tweet appeared to be in response to a customer who complained on Twitter their system hadn't generated a "single watt-hour."

While SolarCity was once number one in the US for residential solar installs, in Q1 of 2019 it slipped to number three below rivals Sunrun and Vivint Solar. Sunrun acquired Vivint in October 2020, consolidating its market share.

During his testimony before the Delaware Court of Chancery on July 12, Musk said Tesla Energy's progress was hampered by the notoriously difficult production ramp on the Model 3 car. Musk said in his testimony and in depositions the company had to pour all its resources into getting the Model 3 to market — meaning its energy operation suffered.

After that, Musk said, the company ran "headlong into a pandemic."

Musk continued his testimony on July 13, and added the global semiconductor chip shortage had impacted production of the Powerwall. He said while demand was around 80,000 units, the company would only be able to make a maximum of 35,000 in the next quarter.

Do you work at Tesla Energy or are you a Tesla Energy customer? Contact this reporter at ihamilton@insider.com or iahamilton@protonmail.com. If you are an employee always use a non-work email.