U.S. e-commerce sales totaled $165.4 billion in 2010, up 14.8% from $144.1 billion 2009, according to non-adjusted estimates released today by the U.S. Commerce Department.

The numbers also show that e-commerce is taking a bigger slice of the overall retail sales pie and is growing far faster than retail sales. 4.2% of total retail spending took place online during 2010, up from 3.9% in 2009, according to Commerce Department estimates. When excluding sales in categories not commonly bought online—automobiles, fuel, grocery and foodservice sales—Internet Retailer calculates that e-commerce accounted for 7.6% of total retail sales during the year, up from 7.0% in 2009. Total retail sales, which includes e-commerce sales, increased 7.0% in 2010 and totaled $3.92 trillion.

Seasonally adjusted, 2010 e-commerce sales were $164.6 billion and represented 4.2% of total retail spending.

E-commerce’s strong fourth quarter helped drive this growth. Q4 2010 seasonally adjusted e-retail sales totaled $44.1 billion, up 16.1% from $38.0 billion a year ago. In contrast, total retail sales were up 8.1% from Q4 2009. E-commerce represented 4.3% of all retail spending during Q4 2010, up from 4.0% a year ago.

Without the seasonal adjustment, Q4 e-retail sales totaled $52.6 billion, up 16.3% from $45.2 billion a year ago. E-commerce represented 4.9% of total non-adjusted retail sales during the quarter. When excluding sales in categories not commonly bought online, Internet Retailer calculates that e-commerce accounted for 8.5% of non-adjusted total retail sales during the quarter, up from 7.8% in 2009.

The full-year and quarterly estimates from Commerce are higher than those released last month by comScore Inc., which reported total e-commerce sales grew 9.8% during 2010 and 11% during the fourth quarter. ComScore draws on online purchase data from its panel of about 1 million U.S. online shoppers. Commerce Department estimates are based on a quarterly survey of more than 11,000 U.S. merchants.