There was a flurry of activity in the solar world last week, particularly in U.S., where companies geared up for the summer solar bonanza prior to Independence Day. The speed at which things in the industry are changing may be best summarized by a new solar installation at the Infineon NASCAR race track. Residential companies stepped up their marketing efforts with new programs, for instance. Some of the other news was choppier, however. While mayors from across the country discussed the importance of clean energy to their jurisdictions, Oregon considered reducing solar incentives there to help reduce their impact on the state’s coffers.

Last week, One Block Off the Grid said its group purchasing discounts and partnerships with SunEdison and local installers, Corbin Electric, are allowing the company to offer solar installations to homeowners at an installed cost of $4.18 per watt in New Jersey. The company said it’s the lowest price for residential solar anywhere in the country, and the systems include Enphase microinverters, which usually add more costs to a system.

Across the country, SunRun, a company that offers its solar power service, akin to a leasing or power-purchase agreement, in an increasing number of states, said it would give $1,000 to the Southern California Sierra Club for each chapter member that installs a system through SunRun. Sierra Club chapters in Northern California and in Oregon have made similar deals with local installers.

Astrum Solar, another residential solar company, operating primarily in the Northeastern U.S., but stretching as far west as Michigan, gained an equity investment from Maryland-based Constellation Energy (NYSE: CEG). The investment will help Constellation increase its support of residential solar projects and will support Astrum’s continued expansion.

The majority of giant utility-scale projects have been announced in the U.S. Southwest, in states like Arizona, California, Nevada and New Mexico. But last week, National Solar Power announced finalist locations for a 400-megawatt photovoltaic project in the Southeastern U.S. The company named seven sites in three states, Florida, Georgia and North Carolina, as potential hosts for the ambitious project. It’s likely to have more development in the region as well. In all it has 3,000 megawatts of contracts signed for the region.

The Infineon Raceway in Sonoma, Calif., last week switched on a 350-kilowatt photovoltaic array that’s providing about 41 percent of its power needs. The array was placed on a high-visibility spot, so NASCAR fans can see the array from the grandstand, according to the raceway.

Oregon’s legislature passed legislation to reduce the Business Energy Tax Credit (BETC) and its residential cousin to help plug the gap in the state’s budget. Oregon Gov. John Kitzhaber (D) was expected to sign the bill, H.B. 3672 into law.

Meanwhile, mayors from across the country gathered for the annual U.S. Conference of Mayors, held in Baltimore, Md., last week. During the conference, mayors discussed a recent survey about the importance of clean energy projects to their towns and cities. Among the results, 46 percent of mayors thought that solar energy had the most potential locally, and 42 percent of cities already had deployed some sort of solar energy in their locality.

The Department of Energy (DOE) last week issued its biggest set of conditional loan guarantees to one company to date. It awarded First Solar (NASDAQ: FSLR) loan guarantees to support $4.5 billion in solar projects, all of which are expected to start construction by October, the company said.

Image courtesy of the Northeast Sustainable Energy Association.