what size pump do i need?

[libby]

We are putting in a new 15x30 in ground vinyl liner pool. We have had some installers tell us that we only need a 1hp pump and others offer a 2hp pump. Some have said that 2hp is just wasting electricity and costing us extra money. We want to get the CORRECT size for our pool. It will be 3' on the shallow end and 6' on the deep end. Again 15x30.

What is the correct size pump for our pool ? Also is a 300lb sand filter the correct size?

Thanks!

Libby