How low can the cost of solar go for residents at this point? Pretty low, according to PV Solar Report’s latest data on solar prices in California. The report, which is based on California Solar Initiative (CSI) reporting and other data, found that HelioPower was installing photovoltaics for an average installed per watt rate of $5.55 at the end of February 2012.

The report found that the average price for installed solar was $7.82 per watt and the highest price was $12.57 as of March 14, according to HelioPower. Using that math, a 5 kilowatt home system would cost $27,750 from HelioPower and $35,100 more—$62,850—from the most expensive installer in the report.

The company does much of its business through SunRun power-purchase agreements, according to HelioPower spokesperson Glenna Wiseman. The company partners with SunRun to finance projects and sets its prices based on what it can get from its manufacturer partners.

“HelioPower is by far the value leaser among the top 15 companies,” said PV Solar Report Managing Director and Founder Stephen Torres. “It changes month-to-month, but you can tell who the value folks are. The higher price-per-watt folks are typically a little smaller; they have their own leasing arrangements or are selling smaller systems.”

HelioPower wasn’t the busiest installer on the list; it was right in the middle, so it’s not just about economy of scale.

“It’s about how we price our projects, we’re looking to price very fairly,” said Wiseman. “We make sure we’re doing enough volume with our PV manufactures and suppliers that we pass those savings along to our homeowners and customers.”

The company is working to drive down system, installation and hard costs of equipment.

Homeowners have been able to get better deals by checking out multiple installers, according to Wiseman—even among those that offer the same power-purchase agreement financing through SunRun.

“There are homeowners that contact multiple SunRun providers and then pit them against each other,” she said. That has helped them get the best deal on their system.

Having resources like PV Solar Report and CSI helps.

“The whole goal is to increase homeowner awareness, to make decisions about purchasing a system, looking for price per watt and getting a good value,” Wiseman said.

After all, once homeowners sign a lease or power-purchase agreement, they are making an agreement that affects their energy bills for years to come.