Commercial · Garner
Distribution warehouse, demand charge focus
A 312 kW rooftop array chosen on interval data, not on available roof area.
- Array312 kW DC
- Modules710 x 440 W
- MountingBallasted, TPO membrane
- Added dead load4.1 lb per sq ft
Record
Full specification
- Array
- 312 kW DC
- Modules
- 710 x 440 W
- Mounting
- Ballasted, TPO membrane
- Added dead load
- 4.1 lb per sq ft
- Energy offset
- About 46 percent
- Billed demand cut
- About 18 percent
The problem
The roof could have carried well over 500 kW. The interval data said not to. Facility load peaked between 1 pm and 4 pm in summer and dropped sharply after the last shift left, so generation beyond about 320 kW would have exported at a rate far below the retail energy charge.
The structure was a 1998 bar joist roof, which needed a structural review before any ballast went on it.
What we did
Sized the array against the summer afternoon load shape rather than the roof, landing at 312 kW DC.
Structural engineer confirmed capacity for 4.1 lb per sq ft additional dead load with ballast distributed away from the mid span of the longest joists.
Ballasted racking on the TPO with slip sheets, so no membrane penetrations and no argument with the roofing warranty.
What happened
Roughly 46 percent of annual energy consumption offset, and about 18 percent off billed demand across the summer months.
Production reporting reconciles to the utility bill each quarter, which the finance team asked for before signing.
Storage for further peak shaving is now under review for the next budget cycle.
Maximum roof coverage is a sales metric, not an engineering one. Sizing to the load shape produced a better return on a smaller array.
Next
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Send twelve months of kWh and a roof photo. You get a sized system, a production model and a payback figure before anyone comes out.
No pressure appointment. The site check is free and the design is yours to keep.