Chicago winters are cold and windy off the lake, and summers are warm and humid. The city has a large stock of older masonry buildings.
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Service types
Site assessment
Shade, roof age, structure, and electrical service, before anyone talks about a system size.
Roof-mounted systems
How an array is attached, flashed, and warranted relative to the roof.
Equipment questions
Modules, inverters, and monitoring. Ask what is specified, not what is typical.
Permits and interconnection
The building permit and the utility's permission to operate.