E-mail has made paper printouts obsolete in most cases and just about every hotel has a business center with a printer, so why would anyone need a portable printer?

Most people don’t, but there are some professions where it comes in quite handy. “The people who really need a mobile printer are people who are doing something on the road and need a document right on the spot,” says Ken Weilerstein, vice president of research for print markets for Gartner, a Stamford, Conn. IT research firm.

Such instances include financial advisors, insurance reps, lawyers -- anyone who needs to produce a document on the fly for signing purposes or to leave something with a customer (as a realtor might do with a set of specs on a house.) Why not just use a hotel’s business center printer? “They might be 10 blocks from their house,” Weilerstein says of the potential user. “There’s a lot of important business that gets transacted in people’s living rooms.”

Options for portable printers

Those in the market can find a decent range of options. Standard battery-operated portable printers from Canon and Hewlett-Packard are the size a lunchbox and a weight of 4.5 lbs. But the Polaroid PoGo Instant Printer is literally the size of a wallet. While the entry costs aren’t too steep -- you can get one for $200 or so -- the operating costs can run about four times that of a laser printer for an average of about four cents a page. As with all printers, the initial cost is just one piece of the overall outlay -- those replacement ink cartridges can add up.

There are other trade offs for a smaller form factor as well. Though the motors for these printers have improved dramatically over the past few years, they’re still not as fast as, say, a laser printer. And they are usually limited to a paper size of 4 x 6, 5 x 7 or, in the case of the PoGo, 2 x 3 inches. But battery life is fairly decent -- Hewlett-Packard’s HP OfficeJet H470 mobile printer can print up to 480 pages on a single charge while Canon’sPixma iP100 can go up to 280 pages on a charge. In light of such limitations, the appeal is really limited to those who need to print on the fly.

Brother also has a whole line of portable printers, including ultra lightweight varieties, which can fit in the pocket. “It’s essentially a niche,” Weilerstein says of the market.

Printing without a laptop

Another related niche is portable photo printers, which appeal to photographers, contractors and real estate agents, among others according to Chris Sabin, product manager for Epson’s PictureMate line. “It’s a nice way to put something right in someone’s hands,” Sabin says. Such printers also appeal to those who don’t store everything digitally. “A lot of people still keep hard copy files,” he says.

Since they don’t need a laptop, such printers are even more portable than standard mobile printers. A 3.6-inch display on Epson’s models, which work off memory cards, let users see what they’re about to print.

Photo printers are a niche within a niche, Weilerstein says. “It really is in a business sense something you’d use in a very specific situation,” he says.