| Scenario | Size (kW) | Utility Fees | Upgrades | Civil | Contingency |
|---|---|---|---|---|---|
| Commercial rooftop | 120 | $2,300 | $6,500 | $2,800 | 7% |
| Industrial behind-the-meter | 750 | $7,500 | $22,000 | $12,500 | 8% |
| Ground-mount feeder impact | 2,500 | $18,000 | $95,000 | $48,000 | 10% |
O&P = Installable × O&P%
Contingency = PreContingency × Contingency%
Total = PreContingency + Contingency
UnitCost = Total ÷ kW_AC
- Enter the system size in kW AC and select voltage class.
- Choose the interconnection path that fits your review level.
- Fill known utility fees, studies, and witness testing costs.
- Add equipment allowances for metering, protection, and upgrades.
- Capture trenching, overhead extensions, and restoration allowances.
- Set admin, O&P, and contingency percentages for your risk level.
- Press calculate to see totals and unit cost above the form.
- Download CSV or PDF to share with stakeholders.
Interconnection cost drivers
Interconnection budgets depend on utility review scope, feeder conditions, and protection rules. Application and study fees are usually predictable, but upgrade responsibility can shift between the utility and the project. Use this calculator to separate utility fees, installable equipment, and civil scope so you can see where risk concentrates. Track total cost and cost per kW to compare projects consistently during procurement planning.
Study pathway and schedule
Projects that qualify for simplified review often avoid extensive system impact studies and shorten timelines. Complex pathways may add supplemental studies, rework, and repeated witness testing. The path factor in the model helps you explore schedule-driven cost growth without changing every line item. Align estimates with milestones such as application, study completion, interconnection agreement, construction, and permission to operate.
Equipment and protection allowances
Metering packages, relays, and switchgear are influenced by voltage class and the point of common coupling. Medium and high voltage interconnections typically require tighter settings coordination, more testing, and larger disconnect ratings. Maintain allowances for transformer or service upgrades until the utility issues formal requirements. Include telemetry, communications, and commissioning labor when real-time monitoring or curtailment is mandated.
Civil scope and constructability
Trenching, overhead extensions, and restoration are often underestimated during early design. Track trench length, unit rates, and surface restoration separately to reflect site constraints. If the route crosses pavement or utilities, increase the restoration allowance and contingency to protect the construction budget. Consider traffic control, dewatering, and right-of-way permits where work impacts public corridors or sensitive surfaces.
Risk, markups, and reporting
Utility administration, contractor overhead and profit, and contingency should match your contracting strategy and uncertainty level. Apply higher contingency when interconnection requirements are not confirmed or when schedules are tight. Export the estimate as CSV or PDF to document assumptions, escalation, and inclusions, then update values as studies conclude and quotes arrive. A disciplined change log improves stakeholder confidence and reduces surprise funding requests.
1) What costs should be included in interconnection?
Include utility application and study fees, required metering and protection, service or transformer upgrades, communications or telemetry, civil routing work, inspections, and realistic markups for administration, overhead, and contingency.
2) How do I choose the interconnection path?
Select the path that matches expected review complexity. If the utility indicates screening only, use fast track. If system impact is likely or uncertain, use standard or complex to avoid under-budgeting.
3) Why does voltage class change the estimate?
Higher voltage interconnections typically need more protective functions, additional testing, larger switching equipment, and tighter coordination. Those requirements increase both equipment allowances and commissioning effort.
4) Where should contractor overhead and profit apply?
Apply overhead and profit to installable scope such as equipment, civil work, and permitting tasks. Utility fees may be pass-through items, so apply markups only if your contract structure requires it.
5) What contingency percentage is reasonable?
Use higher contingency when utility requirements are not finalized, routes are unknown, or procurement is early. As studies and quotes arrive, reduce contingency and move uncertainty into confirmed line items.
6) Can I share results with stakeholders?
Yes. After calculating, download the CSV or PDF report. Share the file with owners, engineers, and reviewers to confirm assumptions, align scope boundaries, and document updates through each milestone.