Image source: Tesla Motors.

Electric-car and energy-storage company Tesla Motors (TSLA -1.92%) just moved one step closer to fulfilling its vision to provide a complete sustainable energy solution for customers. The U.S. Federal Trade Commission announced on Wednesday it granted Tesla permission to acquire solar-panel company SolarCity (SCTY.DL) -- a deal Tesla began working on in June. 

Here's what investors should know.

The details

Listed on the FTC's website as one of Wednesday's "early termination notices," the FTC said it had granted Tesla permission to acquire SolarCity. The approval happened quickly and with less scrutiny than some mergers because the two companies operate in different businesses.

Tesla first announced its proposal to acquire SolarCity on June 21, but the two companies didn't actually reach an agreement to combine until August 1. Typically, a potential acquisition doesn't become public until two companies have reached an agreement. But Tesla and SolarCity opted to be more transparent because of the common major shareholders between both companies.

The most notable common major shareholder is Tesla CEO Elon Musk, who is the largest shareholder and chairman of both companies. Musk also recused himself from voting for the deal.

Tesla Powerwall. Image source: Tesla Motors.

Tesla is particularly interested in SolarCity because it's already producing energy storage products; it wants to offer a better value proposition for customers as a combined entity. "Solar and storage are at their best when they're combined," Tesla said in a press release about the deal earlier this month. Tesla explained further:

As one company, Tesla (storage) and SolarCity (solar) can create fully integrated residential, commercial and grid-scale products that improve the way that energy is generated, stored and consumed.

...

By joining forces, we can operate more efficiently and fully integrate our products, while providing customers with an aesthetically beautiful and simple one-stop solar + storage experience: one installation, one service contract, one phone app.

The two companies expect to derive $150 million of cost synergies in the first full year after closing, driven by sales and marketing efficiencies and corporate and overhead savings. Further, as an integrated company Tesla and SolarCity believe they can improve the value proposition of energy storage and solar by lowering hardware costs, reducing installation and service costs, improving manufacturing efficiency, reducing customer acquisition costs, and cutting capital costs.

Interestingly, Tesla has intended to provide solar power since Musk laid out the company's "Secret Master Plan" 10 years ago. "No kidding, this has literally been on our website for 10 years," Musk said when he revealed part two to the plan this summer.

What's next?

Despite the FTC's permission for Tesla to acquire SolarCity, there are still hurdles to overcome, namely a majority vote of approval by disinterested shareholders, and the ending of SolarCity's "go-shop" period. In conjunction with Tesla and SolarCity's August 1 agreement to combine, SolarCity was granted a 45-day go-shop period in which it can solicit any alternative buyout proposals. This go-shop period ends in the middle of September.

Tesla expects the SolarCity deal to close in the fourth quarter, so look for an update later this year. As investors wait to see if the deal is official, the deal is starting to look like it's in the bag.