Wells today usually are drilled with at least an 8.75-inch wide hole and a submersible pump slides in place easily along with the piping and electrical wires. Hole size varies depending on conditions and the choice of the driller.
A one-half to three-quarter horsepower pump is the most popular selection. But in some cases, where additional water quantity is needed or the well is deeper than usual, a larger pump may be needed.
To abstractly select a larger horsepower pump with the thought that bigger must be better may be mistake. If the pump transfers too much water too quickly from the hole it might deplete the ground water in the immediate vicinity of the pump and run out of water. The tell-tale sign of this problem is no water being produced .
Talk to a licensed, certified pump installer when making decisions on pump size.