Who won the last round in the rooftop solar battle? Weighing in at a market cap of $3.72 billion, it's SunPower (SPWR -4.14%), that's who.

In its most recent coup, residential solar panel installer SunPower struck a deal with Meritage Homes (MTH 0.12%), one of the ten largest homebuilders in the United States. According to Builder Online, Meritage Homes will be making the announcement in the next couple of days. The deal is part of Meritage's national new-home solar program. This finds SunPower one step closer in attaining its goal of doubling its residential and business customers from 150,000 in 2012 to 300,000 by 2015.

Of course, the deal means nothing if Meritage is not selling homes, but based on last week's earnings release for the fourth quarter and full year 2013, it seems that the company is on the right track: Q4 2013 was Meritage's eleventh consecutive quarter of year-over-year growth in home orders. Also of note, Meritage's ending backlog of 1,853 units for the twelve months ended Dec. 31, 2013 is a 26% improvement over the 1,472 units it had in backlog for the same period ending in 2012.

SunPower has already partnered with some other industry leaders, such as KB HomeLennar CorpStandard Pacific Corp, and PulteGroup

Signs of a brightening housing market
The nation is far from claiming that it is out of the woods in terms of the housing crisis, but there are indications that things are taking a turn for the better. Specifically, new home sales are improving. According to recently released data from the Department of Housing and Urban Development, 428,000 new homes were sold in 2013, which is 16.4% above sales in 2012 and the highest level in five years. Certainly, this bodes well for SunPower's partnerships with new home builders.

Although skeptics may argue that entering into these agreements will not yield anything substantial, they must consider the following: According to a new report from McGraw Hill Construction, green homes represented 23% of new home construction in 2013, and this is expected to rise to between 26% and 33% of the market by 2016. In other words, this is an increase from $36 billion in 2013 to between $83 and $105 billion by 2016. To further validate the company's interests in courting homebuilders, the study also revealed  that 68% of builders found that their customers are more willing to pay for green houses while 51% of builders and remodelers believe that it's easier to market green homes -- an increase from 46% in 2012 and 40% in 2008.

Who's snapping at SunPower's heels?    
SolarCity (SCTY.DL) is the main culprit. The company recently struck a deal with Taylor Morrison Homes (TMHC -0.97%), who will now offer homebuyers the option of adding on services from SolarCity. Homebuyers can equip their new homes with a 5.5 kilowatt solar array for which SolarCity will provide solar installation, insurance, monitoring service and repairs for the duration of the 20-year contract.

There are several partnerships SolarCity has made with other homebuilders. Oakwoods Homes in Denver is one; Shea Homes in Arizona is another one. Marnella Homes in Oregon is one of twenty homebuilders with whom SolarCity has formed partnerships. These partnerships, in addition to the residential customers not affiliated with new home builders, make SolarCity the leader in the residential market. The company is set to release Q4 2013 earnings toward the end of February, but according to its prior release, it will deploy approximately 278 MW in 2013, and it's guiding to deploy between 475-525 MWs in 2014.

SunPower, on the other hand, installed 16 MW of North American residential capacity. The caveat, though, is that SunPower also operates internationally and in the commercial and utility-scale markets. As a result, SunPower is guiding to have between 1,000 and 1,030 MWs recognized for FY 2013.

Foolish final words... 
Will this move the needle for SunPower? In all likelihood, the answer is no; however, I find it compelling that SunPower is keeping pace with SolarCity (if not inching ahead) in the race to secure deals with home builders. 

When considering either company for investment, one must naturally dig much deeper. I find both companies equally intriguing, and they are certainly at the top of my watch list for a variety of reasons other than the deal with home builders they have under their belts.