We predict the saturation phase of building-integrated photovoltaics (PV) for which complexsystem model coupled with electric power flow analysis are carried out. The detailed power flow analysis determines the probability of reverse current occurrence due to the additional PV installation in a twodimensional 6.6 kV-scale distribution network consisting 2500 grid-connected individual customers. The agent-based simulation including the customer agent and government agent describes the time-dependent behavior of the PV penetration in an artificial society. Growth of the building-integrated PV is assisted by a battery installation as a reservoir for the reverse current. However the excessive promotion for the PV penetration by the government results in increase in the cost of reverse current care.