Based on the load you want to run with inverter can calculate the size of inverter an battery.
Exmp. 5nos. of 20 watt CFL, 3 nos. of 60 Watt fan & One TV 200 watt & 1000 watt AC want to run with inverter. The total load are (20x5+3X60+200+1000) 1480 watt, hence based on the load consider 20 to 30 % of conversion margin (1480X1.2= 1776Watt or 1.78kW) than the select the available standard size nearest to your load. 2kW Inverter would be sufficient to your hoe load.