Source: Google Green Blog.

What does Alphabet spell out for Google (NASDAQ: GOOG)? It's what everyone who follows the company has been asking since the announcement of the company's restructuring. More driverless cars and the like? Well, Google may have just tipped its hand.

This week, the search giant announced Project Sunroof. Only available in San Francisco, Fresno, and Boston at the moment, the service allows customers to enter their addresses and, after some Google magic, learn how much they would save if they went solar. Is this just another app to be featured besides Translate and Maps, or is it a step toward bringing clean energy directly to consumers?

On the Google Green Blog announcement, the company revealed that the service "can help connect you with local solar providers." Will Google be able to monetize the project by linking customers with installers, or is there another route? Let's take a look at the company and some of its experience in solar energy.

Alphabet's ABCs
On the Official Google Blog, Larry Page, Google's CEO, explains the restructuring. "Alphabet is mostly a collection of companies. The largest of which, of course, is Google." The other companies under the Alphabet umbrella will take on more ambitious opportunities -- the company's work in Life Sciences and the development of a glucose-sensing contact lens for example.

There are many other projects on which the company is working, and the number may be increasing: Research and development costs accounted for 15.7% of the company's revenue in the second quarter -- a 24.6% increase over those costs in the first quarter. Perhaps, in the Google Labs somewhere, there's a solar project incubating -- one that relies on the implementation of Project Sunroof before it can be born.

Already warmed up to the idea
Project Sunroof isn't Google's first foray into the residential solar market. In 2011, Google announced a partnership with SolarCity (NASDAQ: SCTY) in which the search giant would invest $280 million "to create a fund that will help SolarCity finance more solar installations across the country" -- a fund that surely helped propel SolarCity closer to its goal of one million customers by 2018.

This, the first of Google's investments in residential solar, was also its largest investment in renewable energy at the time. In commenting on the deal, Rick Needham, Google's Director of Green Business Operations, acknowledged that it wasn't just a deal to garner some positive public sentiment; he suggested further deals like this were likely in the future: "Google has made a series of investments in renewable energy because they make business sense and help deploy a range of solutions that can help move us toward a clean energy future."

Three years later, in 2014, Google teamed up with SunPower (NASDAQ: SPWR) to create a fund that would make it easier to finance the purchase of residential solar systems. In essence, Google purchases the homeowners' systems, than sells the power back to the homeowners at a rate cheaper than their utilities charge.

According to SunPower's press release on the deal, "Thousands of homeowners are expected to finance solar power systems through SunPower solar leases as a result of this program." At the time, SunPower stated it had about 20,000 residential customers.

Based on those figures, Google helped SunPower significantly expand its residential customer base. Representing 47.5% of its revenue in the second quarter, the residential market is important to SunPower. The company operates in three markets: residential, commercial, and utility-scale. It is the residential market, though, which is the most profitable; for the second quarter, the residential market had the highest gross margin of all three segments, at 23.3%.

A sunny forecast
Residential solar is a growing market, and industry analysts expect the trend to continue. According to a recent report from the Solar Energy Industry Industries Association and GTM Research, in Q1 2015, the residential solar market had its largest quarter ever, growing over 11% quarter over quarter from Q4 2014. Furthermore, the report forecasts the solar market to grow 27% over its 2014 level in 2015, with residential solar accounting for the fastest growth.

Analysts are cautious to forecast the rapid growth of solar to continue over the next few years, as state and federal tax incentives are uncertain, but don't forget SolarCity, and what it believes is a very attainable goal: one million customers by 2018.  

The Foolish takeaway
Although Project Sunroof is only available to residents in three cities, Google plans on expanding its availability to other markets in the coming months. Having already partnered with industry-leading installers SolarCity and SunPower, Google has gained a foothold in the residential market, demonstrating its recognition that the market is ripe for investment.

Project Sunroof may be just another step in the company's journey to bring solar to homeowners' rooftops and profits to investors' portfolios.