The world's largest retailer set the target, which roughly doubled its previous annual sales, late last year as part of a series of green policies. It expanded shelf space, cut prices and ran ads for the swirly compact fluorescent bulbs, or CFLs.
Environmentalists and manufacturers said Wal-Mart's push has helped boost national demand for the efficient bulbs.
Backers including the U.S. Environmental Protection Agency say CFLs use one-third the energy of a traditional incandescent bulb, last up to 10 times longer and save $30 or more in energy costs over their lifetime.
Last year, an estimated 150 million CFLs were sold nationally, and the number may be twice that this year thanks to Wal-Mart's contribution, said Noah Horowitz, senior scientist with the Natural Resources Defense Council.
Less than 10 percent of light sockets in North America have a CFL rather than a traditional bulb, up from 2 percent three years ago, according to manufacturer Philips Lighting, a division of Royal Philips Electronics NV.
Wal-Mart's executive in charge of environmental strategy, Andrew Ruben, said the 100 millionth CFL was sold over the weekend at one of Wal-Mart's roughly 4,000 U.S. stores and Sam's Clubs.
Wal-Mart achieved the target by raising awareness of CFLs and lowering prices, Ruben said.
Wal-Mart worked with suppliers to reduce CFL prices by about half, to around $1.65 per for the equivalent of a 60-watt incandescent bulb from around $2.40 a year ago. That compares to about 24 cents for the incandescent bulb.
It raised awareness by expanding shelf space for CFLs as well as promoting them in-store, in ads and through campaigns with other groups.
Wal-Mart has not yet set a new target for CFL sales.