Disclaimer

This is not a permit calculation, a utility approval, or a substitute for a licensed electrician, HVAC contractor, or the authority having jurisdiction. Panel Headroom is an independent educational site. It is not a utility, a certification body, or a contractor. Electrical and generator work that is done incorrectly can cause fire, shock, or carbon monoxide poisoning. Use the adopted electrical code and manufacturer instructions; pull permits where required.

What you may not treat these pages as

• A load calculation for a permit, a utility interconnection, or an inspection.
• Engineering, electrical, or HVAC professional advice.
• A finding that your panel, generator, or heat pump is “approved,” “up to code,” or “safe to install.”
• A quote, an energy audit, or a Manual J heating and cooling load.
• The text of the National Electrical Code. NFPA 70 is a copyrighted standard. We describe public, high-level method structures and cite article numbers where they help a homeowner talk with an electrician. We do not reproduce copyrighted tables.

Safety

Incorrect electrical work can cause fire, shock, or death. Backfeeding a generator into a panel through a dryer outlet or an unlisted cord can energize utility lines and kill a line worker. Portable generators produce carbon monoxide, which can kill in minutes if the unit is run in a garage, basement, or too close to an opening. Follow CPSC and CDC guidance, including placing a portable generator outdoors and at least 20 feet from the house.

Data and typographical errors

Sources can be revised, jurisdictions adopt different code editions, and we can make mistakes. If a number here disagrees with a nameplate, a utility bill, or the adopted code, those documents win. Please use the contact address on the About page once it is monitored.