Elon Musk wants to merge Tesla and SolarCity into a single "end-to-end" clean energy company that would handle everything from solar power to batteries to electric cars. He calls it a "blindingly obvious" move. But plenty of investors are far more skeptical.

The backstory: On Tuesday evening, Musk’s Tesla Motors made an offer to buy SolarCity — the big solar installer he also founded — in a $2.8 billion deal. The goal, Tesla said, was "the world’s only vertically integrated energy company offering end-to-end clean energy products to our customers."

Tesla is an automaker that currently specializes in high-end electric vehicles. The company is pinning its hopes on the Model 3, a mass-market electric car scheduled to come out in December 2017 that will initially sell for $35,000. Tesla has also become deeply invested in batteries, building a $4 billion Gigafactory in Nevada and offering Powerwall storage systems for homes and businesses.

SolarCity, meanwhile, is another company Musk helped start that is run by his cousins Lyndon and Peter Rive. It's still the largest rooftop solar installer in America, but it’s struggled lately against rising competition, and share prices have plunged 64 percent in the last 11 months. SolarCity has also been branching out into efficiency and other energy services and has plans to manufacture solar panels in a forthcoming factory in Buffalo.

Both companies are growing rapidly, but neither is currently profitable. Tesla lost $889 million in 2015 (with revenues of $4 billion), and SolarCity lost $769 million (with revenues of $400 million). While it seems perverse to lump two unprofitable companies together, Musk is hoping there’s an opportunity for fruitful collaboration here. The downside, however, is that there are huge risks.

How Tesla and SolarCity might work together

Under the terms of the proposed deal, Tesla would acquire all of SolarCity's outstanding shares of common stock in a swap, offering the equivalent of $26.50 to $28.50 per share. That's 21 percent more than SolarCity shares were trading for at Tuesday's close.

The idea, it would appear, is to create a clean energy superpower. Here’s a key passage from Tesla’s post:

We would be the world’s only vertically integrated energy company offering end-to-end clean energy products to our customers. This would start with the car that you drive and the energy that you use to charge it, and would extend to how everything else in your home or business is powered.

In the call, for example, Musk mentioned that people could walk into a Tesla store and buy solar panels. If that was the only big change here, a merger would seem rather small and pointless. But in its post, Tesla hinted at some more subtle ways the partnership could matter:

We would be able to maximize and build on the core competencies of each company. Tesla’s experience in design, engineering, and manufacturing should help continue to advance solar panel technology, including by making solar panels add to the look of your home. Similarly, SolarCity’s wide network of sales and distribution channels and expertise in offering customer-friendly financing products would significantly benefit Tesla and its customers.

Over at Utility Dive, Gavin Bade points out that a company with Tesla’s battery knowhow and SolarCity’s solar expertise could partner with electric utilities on major solar-plus-storage projects — and branch out from there into other services for grid operators. "I think we’ll likely see quite a lot of partnerships with utilities, and we see our business growing [there] quite significantly," Musk said.

That could prove a fruitful synergy — at least in theory. America's grid is changing rapidly, and solar power, electric cars, and battery storage are all quite likely to play a key role in that evolution going forward. No one knows which business models will prevail just yet, but a Tesla/SolarCity partnership would at least be decently positioned here.

Note that this merger isn't final and still needs to be approved by shareholders. Musk said he would abstain from voting since he sits on the boards of both companies. (He owns 22 percent of SolarCity and 21 percent of Tesla, so there's an obvious conflict of interest here.)

There are also big potential downsides to the deal

One huge risk here is that acquiring SolarCity could potentially muck up Tesla's plans to build the Model 3. Tesla is taking on about $2.8 billion worth of debt in the deal, right at a time when it needs to raise a large amount of cash to ramp up production of a mass-market car.

A few analysts, like Edward Niedermeyer, have been skeptical that Tesla will succeed with the Model 3 — the required skill set to create a reliable, mass-market vehicle is way different from anything the company has shown today. Now here's another potential hurdle to overcome.

Some analysts have also wondered if the real reason for this move was to prop up SolarCity, which has been ailing of late. The company's stock price has been sliding this year, partly due to concerns about its debt load and partly because it was hurt by regulatory changes in Nevada that throttled the rooftop solar industry. And its last earnings report was disappointing.

In recent months, the Wall Street Journal has been probing the peculiar ways in which Musk uses his companies to prop each other up. For instance, when SolarCity needed to raise money in October 2014, it offered "solar bonds" to investors. About half of them were bought up by SpaceX — another Musk-owned firm that's engaged in private spaceflight.

Here is Elon Musk & Family Inc. (Tesla, SolarCity and SpaceX) pic.twitter.com/qkh49oLVtx — Scott Austin (@ScottMAustin) June 21, 2016

If Musk is primarily making this move to prop up a failing company, the logic becomes much, much less compelling. We'll see how investors react — and if any shareholders object to one of Musk's companies buying up another in the coming days.