The best way for any professional solar PV designer to custom design
the right system for a customer is for the customer to provide the historic
electric consumption for the structure they wish to add solar to. In this
way a system can be sized appropriately to meet the assumed future
demand based on historical consumption and the customer’s needs. In
this way the customer will not buy more than what they need nor buy a
system that is too small either. The goal is to become the owner of a
small power generation system that makes enough clean renewable
energy to power your home or business without over producing and
being forced to sell the extra at wholesale.