Most solar companies set the price according to the solar system's wattage. A solar installation's “cost per watt” is a little like the “price per square foot” when you buy a house.
AC300 paired with the 1× B300 battery module now starts at $2999 (original price is $3699, that is $700 OFF for a limited quantity). AC300 paired with 2× B300 battery modules starts at $4499 ...