SAN JOSE, Calif. ( TheStreet) -- SunPower ( SPWRA) has finally reported its long-delayed fourth-quarter earnings. Did the U.S. solar company deliver? Shares of SunPower were down about 10% in after hours trading. SunPower reported earnings per share of 47 cents. The Street had forecast earnings per share of 49 cents for the fourth quarter, versus 70 cents a year ago. SunPower's fourth quarter earnings were reduced by three cents as a result of its audit investigation into overstated earnings in the previous two years. SunPower had revenues of $548 million, while the Street estimate was for $490 million in fourth-quarter sales. In the year-ago fourth quarter SunPower had revenues of $400 million. SunPower's gross margin was 21.7% in the fourth quarter, lower than its 23.1% margins in the previous quarter and 20.2% margin in the year ago quarter. Margin performance has been a key for solar investors this earnings season. Gross margins on SunPower's systems business went up from 17% to almost 22%, buts its component gross margins were down by 5%, and down by 15% versus the year-ago quarter. What's more, SunPower forecast an average sales price decline of 20% in 2010, going beyond the 10%-15% decline that most solar companies have guided investors to in 2010, in terms of pressure on ASPs. SunPower also guided investors to earnings per share of 5 cents in the first quarter of 2010, versus an estimate of 34 cents from the Street. The Street's full-year estimate of earnings per share of $1.78 was also above the high end of SunPower's earnings guidance, at $1.65. SunPower's total operating expenses in the fourth quarter were $15 million higher than the third quarter, and approximately $20 million higher than second quarter operating expenses. The solar company spent $3.6 million on its accounting investigation and $1 million on expenses related to the Sunray acquisition. These one-time expenses helped pushed SunPower's quarterly expenses above 10% of revenues. The Street's revenue guidance of $2 billion in 2010 for SunPower was in line with the low-end of SunPower's guidance. SunPower said during the conference call after its earnings that it was shifting revenue recognition from the first quarter to the back half of 2010. SunPower said the financing environment for some developers led to a pushback in projects. What's more, the recent accounting investigation pushed fourth quarter projects back as SunPower could not receive financing while having invalid financial statements.