I think budgetprepp-n might mis-understand what you're trying to tell him. If the DC load is 15 amps, you'll draw closer to 17 amps from the battery every hour. If the AC load is 15 amp, you need to multiply the 15 times ten (= 15 amps DC) plus the 10% power loss for the inverter if you're using a 12 volt inverter. As an example, my TV in my motorhome draws 2.3 amps, 120 VAC. By actual measurement, the inverter is pulling close to 25 amps per hour (at 12 volts) from the battery every hour, averaged. If the battery is very well charged, it will take a little less. Since a 12 volt battery is ten times less voltage compared to 120 volts AC, you must multiple the AC amps times ten. On my motorhome, a well charged battery bank (4-6 volt, golf cart batteries (each battery is 115 amp hour) wired 2 in series for 12 volts and then those 2-12 volt banks are wired in parallel to give me 230 amp hours at 12 volts, would operate my TV for about 7 hours (the math says it should be 8.5 hours) before the battery voltage would drop too far and damage the battery.