The two primary electrical concerns during weatherization are insulating homes that contain knob-and-tube wiring and identifying overloaded electrical circuits.

Knob-and-Tube Wiring: Retrofitting thermal insulation around older electric wiring (primarily knob-and-tube wiring) can cause it to overheat, resulting in a fire hazard. States must ensure that insulation around wiring conforms to local codes.

In 1987, an amendment to the National Electric Code (NEC) prohibited the placement of insulation in contact with knob and tube (K&T) wiring. This amendment had a significant impact for low-income weatherization programs around the nation. Retrofitting insulation into sidewalls and attics where K&T or faulty wiring often exists is a major weatherization activity and accounts for the greatest energy savings return on investment. During the summer of 2002, the Pennsylvania Department of Economic and Community Development (PA DCED), the Weatherization Training Center (WTC) at Penn College and STEP Inc., a Weatherization Assistance Program provider, entered into a joint research project. Its purpose was to attempt to identify simple and cost effective wiring retrofits and prescribe safe methods for installing thermal insulation where K&T wiring exists. The report, Retrofitting Knob and Tube Wiring, An Investigation into Codes, Wiring Practices and Cost, provides the results of the project.

Overloaded Electrical Circuits: Weatherization measures that involve the installation of new electrical equipment can bring previously marginal overload problems to hazardous levels. If these problems prevent adequate weatherization, the agency should consider repairing them.