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Most manufactures create "standard efficiency" solar panels, which convert around 15% of the energy that hits them from the sun into electricity, while SunPower's convert over 20%. They also cost significantly more, so in practice SP's modules are usually the most space-efficient, but not always the most cost efficient.

It's a marketing claim by the manufacturer:

http://us.sunpowercorp.com/about/the-worlds-standard-for-sol...

Slightly more surface area, back mirror, etc.

high-er- efficiency

The other commentators are missing what the OP is talking about. The grammar is incorrect.

I agree with them. It's a context issue, not a grammar issue.