Is 100Wh from a standard Group24 battery reasonable?

100 watt hours is 8.3 amp hours at 12 volts. If the 100 watt hour figure is correct, a group 24 battery should be able to handle this easily. For a comparison, running headlights (and taillights) for an hour would consume in the ballpark of 150 watt hours. An hour of furnace run time would be about 85 watt hours. A dual golf cart battery can supply about 2500 watt hours (but it's generally recommended to not use more than half of that before recharging).