Car battery are not mean for solar usage way. It charatistic is to supply high burst amp in short time. But it need to be charge back immediately. It usage cannot be more than 50-60%. Otherwise will be shortlife.  Solar do have lead acid battery called deep cycle battery. It design to be use in steady amp supply with more than 50% can be drain. Last 2 yrs asking the GP deep cycle battery price. Cost RM750-850 for a 100A.   

Lead acid require maintenance to top up and place outside. Seal lead acid , lithium, NiMH etc don't require maintenance. All this require dedicate charger to maintain the charging. So the battery life can be last longer. Lithium ion is getting popular for solar usage. Probably the price is coming down.

This is the solar battery charger which I brought from state. It have efficiency about 90% more if not mistaken. It program to charge few type battery, maintain and monitoring usage.

Off everything and only run air cond or washing machine, taking efficiency at 75%.
If the equipment to be test is 1000W(per hour), running it for 1 hour should be using less than 1 unit. But it moves 1 unit before 1 hour.
Not to mention people that complaint on this. Come out in most chinese paper every now and then.