Chapter 1 · Solar System Basics
1.8.4 Don't measure system size in "number of panels"
90% of homeowners describe their system as "I have X panels on the roof." This phrasing comes from unprofessional or deliberately misleading sales scripts. It is fundamentally wrong.
Panels vary hugely in wattage — anywhere from ~280W per panel to 500–600W per panel, more than a 2x range. Counting panels tells you nothing about system capacity.
We saw a customer who had recently installed a system using outdated 280W panels — and the salesperson kept selling them on "look how many panels you got, your system is huge."
So remember: system size is measured in kW (or kWh for battery storage), never in panel count.