Module Power has been increasing rapidly over the last few years but some of those gains have been a result of larger cell sizes not advancements in technology. Powerclass alone is no longer a good indicator of module value. You will need to look deeper at Power Density to discover how each module will impact the nameplate and cost of the system.
Module Power Density = watts per square foot (w/sq.ft)
Powerclass / module area (L x W)
The examples below clearly demonstrate that modules with varying powerclass can have a very similar power density.
Silfab 330W with surface area of 18.3 sq.ft has a power density of 18.03 w/sq.ft
Brand X 340W with surface area 19.3 sq.ft has a power density of 17.64 w/sq.ft
Brand X 360W with surface area 19.5 sq.ft has a power density of 18.50 w/sq.ft
Two significant implications when choosing a high powerclass but low power density module.
A premium is usually charged for higher powerclass modules even though they don’t necessarily deliver more watts over a given area
Your cost for MLPE (optimizers and micro-inverters) typically increases ($/W) to handle the higher power through each device.
WHAT DOES ALL THIS MEAN?
When you have a limited rooftop area to cover, using a higher powerclass module with a low power density can yield the same (or lower – fig. 1 below) system nameplate but at a higher cost to you the installer. This can hit your bottom line through lower close rates (you are over-priced) and lower margins.