Consumer electronics and apparel will help drive the growth.

E-retail sales in the United States will grow at a compound annual growth rate of approximately 14% over the next four years, topping out at $434.2 billion in 2017, according to a new projection from eMarketer Inc.

The research firm expects 2013 e-commerce sales, excluding travel and ticketing, will reach $258.9 billion, up nearly 15.0% from $225.2 billion 2012. Annual growth rates will taper off slightly each year following: 14.6% in 2014, 14.2% in 2015, 13.6% in 2016 and 12.8% in 2017, eMarketer says.

Mobile devices will play a larger role in generating web sales. The research firm says smartphones and tablets now account for 11% of e-commerce sales. It predicts that share will reach 25% by 2017. EMarketer says it bases its forecasts on historical data from the U.S. Commerce Department and on data and trend analysis from e-commerce experts.

Current and projected sales statistics show strong web sales for products in the apparel and accessories category. EMarketer says e-retail sales of apparel and accessories will reach $54.2 billion this year in the United States, accounting for 20.9% of 2013 total web sales. Only computer and consumer electronics has greater sales and share at $56.8 billion and 21.9%.

EMarketer, however, predicts apparel and accessories online sales will post the strongest compound annual growth rate, 17.2%, through 2017, whereas computer and consumer electronics will grow at a compound annual rate of 15.3%, trailing behind food and beverage (17.0%), books/music/video (16.3%), and toys and hobby (16.2%) categories.  In 2016, apparel and accessories and computer and consumer electronics sales will account for $175.7 billion in web sales, or 45.6% of total U.S. web sales.