Backfeeding a service panel energizes the entire panel and power is distributed throughout the house on all circuits. Only the largest portable generators are capable of supplying enough power for an entire home. Turning some breakers off helps to resolve this issue, but does so without balancing the loads.
The generator supplies 240 volts which is split into two, 120-volt lines. Each line is capable of supplying half the generators capacity.
If all the essential circuits are located on the same line, the unbalanced load puts a strain on the generator and the home can only use half the generator’s capacity.
A Better Solution
A manual transfer switch takes power from the generator and distributes it only to the branch circuits that were selected when the switch was installed. Each circuit has its own breaker, and electrical power is automatically confined to the dwelling. It can never accidentally power the neighborhood utility lines and endanger workers.
The load is balanced because half of the load is assigned to one 120-volt line, and the other half is assigned to the second 120-volt line. The balanced load puts less strain on the generator, saves fuel, and allows utilization of the generator’s full capacity.