Offhand, I'd say you want a larger supply line, depending on whether the drawdown level is 70 feet, or maybe less. Drawdown level gives you the point from which you can read a pump performance curve. You can probably expect at least 20 gpm from the well. The well driller should supply you with all the relevant information. An undersized supply pipe will cost you water pressure, pressure that you're paying for. Any additional cost is a one-time expense. The energy savings are forever. Make it 1 1/2" at a minimum.
A very rough ballpark estimate for an acre lot would be 6 thousand.
