Despite occasional outages, few small-business owners have invested in backup power systems to guard against blackouts and other emergencies, a new survey shows.

Of 450 owners recently polled by Emerson, a St. Louis, Mo.-based technology firm, only about a quarter said they had a backup power supply in place. The majority also didn't have business continuity plans.

The survey found that larger businesses were more likely to have backup power.

Though emergency preparedness was low across the board, 71 percent of respondents expressed interest in installing a backup power system, up from 58 percent in a similar survey conducted five years ago, the firm said. Nearly half said they had looked into backup systems this year.

Nearly all respondents said their companies had experienced at least one power outage last year, with many left without power for more than four hours, the survey found.