22 AH capacity, pulling enough amps for a 1500 Watt heater (125 amps), considering the Peukert Effect, it'll last roughly .07 hours (4 minutes 12 seconds) before it's deader'n a doornail. If it's only a 1200 Watt heater (100 amps), then it'll last .09 hours (5 minutes, 24 seconds).
To run a...