Apparatuses and methods to firewall distributed energy sources. In one aspect, an apparatus includes: a first connector configured to interface with a distributed energy source; a second connector configured to interface with a connection point of an electric power system; at least one switch coupled between the first connector and the second connector; at least one sensor coupled with the switch; and a controller coupled with the at least one switch, the controller to use the at least one switch to selectively connect or disconnect an electric path between the first connector and the second connector based on signals from the at least one sensor.