“Solar installer” search intent mixes homes and plants. Procurement for a factory needs industrial references, not only residential ratings.
Ask in the first meeting
Are design and install on one accountable team? Have they delivered similar plant roofs? Who owns grid paperwork and main-board interconnection?
Require in the proposal
Concept layout, fixing approach, safety method, rough outage window, and a handover list (as-built, test records).
Walk-away signals
Sizing without 12-month bills, no roof survey, or vague warranties with no site conditions attached.