But looking further, Bigcommerce said, it found that nearly 80 percent of online retailers were hard at it at noon. At 3 p.m., about 50 percent were working online.

"The data paints a new picture of the modern- day entrepreneur," said Eddie Machaalani, co-founder and co-CEO of Bigcommerce. "Through daily conversations with our clients and monitoring this trend over recent years, we understand that many of these small business owners are pulling long hours to run their business and work a full- or part-time job on top of that, but these numbers provide us with hard stats and evidence."

Bigcommerce said recent data from the U.S. Department of Labor fueled their theory that online retailers are working while at another job.

The DOL reported "fewer Americans are quitting their jobs and more are staying in the same job longer, as 53 percent held the same job for at least five years. Bigcommerce, on the other hand, is seeing things differently.

"Opening an e-commerce business is relatively easy in today's marketplace," said Machaalani. "These days, all you need is a few minutes, a credit card and an Internet connection to get a fully operational online store up and running. These passionate entrepreneurs show that it's possible to start and grow your own business while also maintaining an additional source of income."

Other data from the survey pinpointed what part of the country hosts the most "moonlighters":

• 33 percent — the largest group of moonlighters — are based in Southern states (with Florida, Georgia and Texas having the highest concentration in the region).
• 27 percent are based on the West Coast (led by Arizona, Colorado and California).
• 24 percent of U.S. moonlighters are located on the Northeast (led by New Jersey, New York, Pennsylvania and Washington, D.C.).
• 15 percent are located in the Midwest (led by Michigan, Illinois and Ohio).