Why should I never plug a generator into a wall outlet?

Because it can backfeed power into the utility lines and kill someone. A generator tied into home wiring without an approved disconnecting device sends electricity back out of the house, putting deadly high voltage on lines that utility crews expect to be dead, according to Purdue Extension. OSHA warns that an improperly connected generator can energize wiring for great distances. Purdue adds that if utility power returns while the generator is connected, the generator can be damaged. Use only an approved interlock or transfer switch installed by a licensed electrician, or run appliances on heavy-duty cords plugged directly into the generator.

Sources

• Using Portable Generators SafelyU.S. Occupational Safety and Health Administration
• Generator Interlocking Circuit Breaker KitPurdue University Extension (4-H Electric)