Some vendors and analysts advise consumers to focus on a printer's page yield (the total number of pages that the machine can produce with a single cartridge), rather than on the amount of ink left unused in a cartridge that must be discarded. "This is the most reliable way to understand the life of a cartridge, rather than the amount of ink, or what might be left over," says Lyra Research's Lippman.

But vendor page-yield estimates don't always match reality, as we discovered when testing printers for another article, "Cheap Ink: Will It Cost You? Using a different set of OEM cartridges and printers, we discovered that one HP black cartridge exceeded its projected page yield (810 printed versus 660 projected), while an Epson model printed just 209 pages, far less than the 335 pages the company estimated it would produce. A Kodak printer generated 480 pages versus a projected page count of 540.

Page yields aside, we have yet to hear a persuasive explanation from a vendor as to why some of its cartridges leave so much ink behind. Even if the waste amount is only a few milliliters, that Page yields aside, we have yet to hear a persuasive explanation from a vendor as to why some of its ;artridges leave so much ink behind. Even if the waste amount is only a few milliliters, that unused liquid could have printed a lot of pages. And ink that doesn't end up on a page will wind up contributing to the toxic stew in local landfills too.