Clear answer, explained.
Commercial solar systems are sized against a facility's annual electricity consumption — not its peak demand or its load at any specific moment in the day. The goal for most projects is to match annual generation as closely as possible to annual consumption, subject to the constraints of available roof area and the local utility's interconnection capacity.
The practical ceiling on system size is set by whichever constraint is more binding: roof area (which determines maximum DC capacity) or available LDC interconnection capacity (which determines maximum AC export). On projects where both constraints allow, the system is sized to cover full annual consumption. Where one constraint limits the system below full offset, the financial model reflects the achievable offset — not a theoretical one.
For facilities targeting full or near-full electricity offset, understanding the building's actual consumption profile before finalising system size tends to produce better results. Where efficiency improvements are planned, the post-efficiency consumption profile is the correct sizing input — not the current baseline. Completed GI installations range from 13.7 kW to 1,270 kW, reflecting the full range of C&I facility types, consumption profiles, and site constraints across the portfolio.
What this means in practice.
- Commercial solar systems are sized against the facility's annual electricity consumption profile — not peak or point-in-time load
- System size is constrained by whichever limit is more binding: available roof area (DC ceiling) or LDC interconnection capacity (AC ceiling)
- Where both constraints allow, the system is sized to cover the facility's full annual electricity consumption
- For facilities planning efficiency improvements, the post-efficiency consumption profile is the correct sizing input
- Sizing to a pre-efficiency baseline produces a system larger than necessary once efficiency measures are in place
- Completed GI installations range from 13.7 kW to 1,270 kW across C&I facility types, provinces, and roof configurations
Best-fit environments.
- You want to understand how commercial solar is sized before requesting a proposal
- Your facility has available roof area and you want to know whether it is enough for a meaningful installation
- You are planning efficiency improvements and want to understand whether to factor them into the solar system size
- Your utility has indicated interconnection constraints and you want to understand how that affects optimal system size
