Don’t forget to consider the impact of rebates, financing, and permitting on system expansion. Paying twice for permits might be avoided if it includes the future expansion. The same may hold true for other requirements, such as interconnection paperwork. If a system is financed or leased, it may be difficult or financially less attractive to use the same method to add to the system size. Plus, the installed cost per watt may be higher for system upgrades.
Some tax credits, utility rebates, and incentives may not be available when increasing the system size, or programs may have changed. In other cases, existing incentives such as renewable energy credits (RECs) may have to be renegotiated.