Fuel-oil generator systems are emergency or backup power systems that convert stored energy in the form of diesel fuel in a tank to usable power in a local power system. Generation capacity is effectively only limited by the quantity of diesel fuel available, which can potentially be replenished indefinitely, making the diesel generator an attractive option for facilities which need a high degree of reliability in backup power systems. Diesel generators typically automatically start and switch online in the event of power failure. Used in tandem with battery systems, the combination can provide uninterrupted emergency power which can be sustained indefinitely.