Quick answer: A modern residential solar panel measures roughly 66–82 inches long, 40–45 inches wide, and 1. A 340W solar panel strikes a balance between efficiency and practicality, making it a popular choice for residential and commercial projects. In this article, we'll break dow HOME / What Is the Size of a 340W Solar Photovoltaic Panel? Key Specs & Applications What Is the Size of a 340W Solar. 340W panels hit the efficiency sweet spot – With 18-21% efficiency ratings, 340W panels offer optimal balance between power output and cost, making them ideal for most residential installations where roof space isn't severely limited. 1 meters (43 inches) in width*, with a thickness of 35 mm. These specs ensu e compatibil ty with most mounting systems while. *Solar panel can also be in parallel system (in parenthesis) for 32V/12A power output. Doing Solar DifferentlyPanels supported by best ballistic materials. Multiple embedded bypass diodes. Ruggedized construction for all environments.