The two companies said the solar sector was seeing a slow improvement, but also admitted the industry has yet to overcome the oversupply problems that have driven prices for panels down by about 50 percent in the past 12 months.
"The industry is seeing a much more balanced picture in demand and supply," said SunPower's chief executive, Tom Werner, in an interview.
SunPower, which posted lower net income and trimmed its full-year earnings forecast to the low end of its previous range, said the financing environment for solar projects was improving, and the average selling price fell less than 10 percent during the third quarter.
The company's forecast narrowed in part because some of its large-scale projects have moved into the early part of 2010, Werner said in an interview.
"The good news there is that we're still sold out and we go in with a very strong pipeline into 2010," Werner said, adding that the company is "better positioned" for the first quarter of 2010 than it was for the first quarter in 2009.
Werner also told reporters during a conference call he saw residential demand strengthening in all markets, but still expected average selling prices of panels to weaken in the fourth quarter.
SunPower shares tumbled 13 percent to $29.05 following the results in extended trade after closing at $33.30 on the Nasdaq.
Demand for systems that turn sunlight into electricity has taken a hit because of the global financial crisis and an oversupply of cells and modules caused by a cutback in Spanish subsidies.
Investors are also now fretting over how much and when Germany's government will cut aid to its solar industry, the world's top market.
Werner said SunPower has always prepared for a decline in solar aid in Germany but noted that Germany is a "great market" even with a change in the country's subsidy.
MEMC Electronic Materials Inc, which produces silicon wafers that are a key component in solar cells, swung to a larger-than-expected quarterly loss but said it saw sequential increase in demand.
MEMC said it expected nearly flat revenues during the fourth quarter as compared to the third an outlook executives at the company said was conservative given the uncertainty over pricing.
The company's shares fell nearly 2 percent in after-market trading on the New York Stock Exchange.
MEMC also announced it plans to acquire privately held SunEdison, which designs, installs and finances solar systems for commercial customers.
Smaller solar power systems maker Akeena Solar Inc posted a narrower-than-expected third-quarter loss as it took advantage of lower panel prices and cheaper installation costs.
But shares of the company closed down nearly 2 percent after it said that installation results in the fourth quarter would likely be similar to those in the third quarter.
Akeena said net sales for the quarter fell 27 percent to $7.7 million, reflecting decline in commercial revenue due to the tight credit market and overall economic conditions.