From Halopedia, the Halo wiki
EnerGuide is a 26th century company creating generators to produce power for facilities running on older power systems. The company is likely Earth-based, since EnerGuide buildings are seen in what appears to be the business district of New Mombasa. Generators produced by the company were used by the UNSC at least in their base Crow's Nest near Voi, during the Battle of Earth in 2552.
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