A 305 watt solar panel is a photovoltaic module capable of producing 305 watts of power under Standard Test Conditions (STC). These panels typically feature 60-cell monocrystalline or polycrystalline configurations and measure approximately 65″ x 39″ in size. These mid-range panels, which were once considered high-efficiency options, now occupy a unique position as the industry has largely transitioned to higher wattage. Trina 570W Solar Panel 132 Cell TOPCon Bifacial NEG19RC. Love these trinAs! 132 cells pack punch. My bill dropped 70% after full pallet. frame feels sturdy against wind. Utilizing 96 next generation SunPower all-back contact solar cells, the SunPower 305 delivers an unprecedented total panel conversion eficiency of 18. 6 inches thick, weighs 40–55 lb, and produces 350–460 watts. The efficiency and reliability make it ideal for utility grid-tied installations including commercial and residential rooftop solar panel systems.