I am restoring a 1946 Chev. fire pumper. The truck wiring is still stock with a top light & siren. A small flasher light on the back rail and thats about it. The rest of the lights, head lights and other is standard much like a regular truck. I to date have not given much though about the over load if any. The only concern would be parade use and running the siren without stopping. ( remember the siren may not be designed for such use either ) I may put an additional six volt battery in as a back up. The amount of overworking the generator would be at a minumn. They used these fire trucks for years without any trouble so ....... a parade or two should not be a problem.