Tesla will need to amass a gargantuan pile of cash in the next two years, says one cleantech analyst.

The electric carmaker's impending merger with SolarCity, which goes up for a shareholder vote in November, will require cash in four key areas, according to a note from Oppenheimer's Colin Rusch.

In total, he thinks Tesla will need to raise about $12.5 billion by the end of 2018.



Specifically, Tesla will need to fund $5 billion to $8 billion (or more) in capital expenditures combining its stationary power business with SolarCity; another $2 billion in capital for the auto unit; as well as cash for working capital and operating lease obligations.

While he has been bullish on solar energy and cleantech in the past, as well as Tesla's auto business, Rusch has expressed concerns about the combination of the two companies. He noted in his analysis published Wednesday night that "we believe investors will be concerned with visibility into the business" and that the way the merged company reports the performance of its varying units will be critical to convincing investors to stay aboard.

Rusch cited lack of disclosure as one of the reasons Oppenheimer has a neutral rating on the stock, despite Tesla's potential to be a "transformative technology company" that could deliver "outsized returns for investors."

Tesla has held multiple equity offerings over the last several years, and earlier in 2016 warned it might need to return to markets for another offering this year.

On Sunday the company's CEO, Elon Musk, tweeted that Tesla will likely not need to raise more cash through the first quarter of 2017, though Rusch told CNBC earlier this week that he thinks it would be prudent for the company to raise money sooner.

Tesla's last held an equity offering in May that raised $1.46 billion.