Yes, 1Hp should be sufficient, but also depends on pump. Better try to understand the discharge charts of pump various manufacturer’s and narrow down your pump selection.
If you are opting a DG, then 1Kva is not enough to handle the starting surge of a 1Hp pump, its always recommended to size the DG capacity more than the connected load. But this also depends on which DG you source, say for example if you are targeting branded efficient models a min higher capacity would suffice, and for non-branded local DG’s much higher capacity is what would be probably you require.
I may be wrong on DG part, but I advice you to connect with DG manufacturer’s as they are the correct set of minds to suggest you this.
All the best.