(MONEY Magazine) – EVERY HOME has mysterious pockets of unpredictable climate—a cold basement, a drafty guest room. But cranking up the heat in the whole house to warm one chilly corner burns fuel and money—which is why a space heater, long thought of as an energy drain, might in fact help you cut heating costs.

All electric heaters are completely efficient (that is, 100% of the energy is converted to heat), and most have settings that range from 750 to 1,500 watts, adequate to heat a good-size room.

But beyond those similarities, no two units are alike. We tested a dozen in a 160-year-old Vermont farmhouse, complete with patchy insulation and original windows, during a single-digit cold snap. The criteria: heating capability, design, value and safety (Did they shut off automatically when tipped over? When a blanket was dropped on top?). We chose these six, each of which was identified by the manufacturer as one of its most popular models.

SOURCES: MONEY research, the companies.