When Should Solar Be Designed Into a New Construction Project?
Schematic design. Every phase after that narrows the options and raises the cost of the same decisions.
Key takeaways
- Most solar mistakes on new construction are coordination failures, not technical ones.
- Nearly all of them are inexpensive to prevent during design and expensive to correct in the field.
- The pattern is the same across building types: the solar scope was not in the room when the roof, the electrical rooms, the structure, and the schedule were decided.
We are asked to review solar scopes on projects at every stage, from entitlement to a week before final inspection. The mistakes repeat. Here are the twelve we see most, roughly in the order they are made.
1. Treating the Energy Code requirement as a plan check item
The requirement is sized from the building, so it exists as soon as the building does. Projects that wait for the energy consultant or the plan checker to flag it have already designed the roof, the electrical rooms, and the structure without it.
2. Designing the roof without the array
Mechanical units, skylights, drains, screens, and amenity decks get placed first, and the array gets what is left: fragmented zones that cannot hold the required capacity cleanly. The fix is a roof plan drawn with array zones, fire pathways, and equipment together.
3. Forgetting fire access pathways
The fire code requires pathways and setbacks on roofs with PV. A layout that ignores them is redrawn at plan check, usually smaller. Pathways belong in the first array sketch.
4. No location for the battery
Most nonresidential and high-rise multifamily buildings require storage. A battery that has no designed room, pad, clearances, ventilation, or fire review becomes a late negotiation with the fire authority. The location should be fixed in design development.
5. Electrical rooms sized without the solar gear
Inverter output, battery interconnection, and utility metering need breaker space, bus capacity, and wall space. When the electrical engineer did not have the solar single-line, the room is too small, and the fix is new gear or a new room.
6. Structural loads added after the fact
Array dead loads, canopy columns, and attachment points are small numbers that still need to be in the structural calculations. Added afterward, they mean reinforcement, a smaller system, or an engineer's letter at the worst possible time.
7. Roof warranty conflicts
Attachments that do not meet the roofing manufacturer's requirements void warranties. The attachment method and flashing details should be selected with the roofer and inspected with the roofer.
8. Filing the interconnection late
Utility review runs on the utility's calendar. An application filed during construction finishes after the building opens. File it during construction documents.
9. Ordering the battery and switchgear late
Lead times on storage and switchgear can exceed the remaining construction duration. Procurement should be scheduled with the equipment submittals, not after the array is racked.
10. Installing after the finishes
A solar crew that arrives after roofing, painting, and ceilings are done runs conduit through finished work and brings trades back to patch. Rough-in belongs with the electrical sub's rough-in.
11. Compliance forms that do not match the system
The Certificate of Compliance, the energy model, and the installed system must agree. A mismatch found at final inspection means a revised model or a revised system when there is time for neither.
12. Nobody owns closeout
Permission to operate, the Certificate of Installation, commissioning, monitoring, and the turnover package each have a dependency chain. When no one owns them, the Certificate of Occupancy waits on paperwork.
The common thread
Every mistake above is the same mistake: the solar scope was not in the room when a decision that affected it was made. The remedy is not more expertise; it is earlier involvement, with a solar partner who attends the coordination meetings and owns the scope through closeout.
Questions
What is the single most expensive solar mistake on new construction?
Designing the roof and the electrical rooms without the solar scope. It leads to redesign, change orders, and in some cases carports that were never budgeted, all to meet a requirement that was knowable at schematic design.
Can these mistakes be fixed mid-construction?
Usually, at a cost. We start with a coordination review to identify conflicts before they reach the field, then sequence the remaining work to protect the Certificate of Occupancy.
