Mistakes in the design phase are expensive to fix after installation. Every system, regardless of size and without exception, should be safely designed. Overcurrent protection devices, disconnects, and proper conductor use make for a safe system. Your dealer should have a current Practicing License, or he must use the services of an electrician with this qualification. This precludes anybody not holding a current Practicing License from opening up equipment for the purposes of bench testing or examination requiring internal inspection.
Renewable energy is real.
It can burn down your home or kill you as easily as the grid. Once the system designer has a specific list of RE equipment, they calculate the system s hardware cost. A good system designer goes back to the load analysis to see if they can do anything more efficiently. The system s designer and user work on the load estimate until the system becomes affordable. A good designer will revise the design until it satisfies the load estimate and the customer can afford all the hardware.