Heated Seats - How Many Amps?

[Randy in Maine]

I am thinking about adding heated seats on the bus. They draw 10 amps each x 2. I have a 70 amp alternator.

How many amps does a bus need to drive down the road?

[Hippie]

I don't think it would be a problem, considering a cigarette lighter draws 10'ish.
Ignition should draw just a few amps. Headlights...what...8 amps?
Mine runs fine on a 35 amp generator. I think the extra amperage is used really to charge the battery faster after cranking.