Panels marketed as 250 W – 36 V typically use around 60 cells and are monocrystalline, which gives them higher efficiency compared to older polycrystalline types. A real example panel spec shows:
250 W peak output
Vmp ~36.8 V
Efficiency ~15.4 % for some 250 W modules of that type. �
ENF Solar
So, if your J SOT panel is a 60-cell monocrystalline module, its efficiency is likely in that range (~15 % plus) — typical for many 250 W panels. �
ENF Solar