Professional Solar Installation: From Permit to First Power — What to Expect

Week 1–2: Site Assessment and System Design

A professional installer begins with a thorough site assessment:

Roof Assessment

• Roof age and remaining life (most installers won't mount on a roof with <10 years remaining)
• Structural check: rafter size, spacing, sheathing condition
• Pitch and orientation (south-facing at your latitude is optimal)
• Shading analysis using Aurora Solar or PVSyst across all months

Electrical Assessment

• Main panel amperage and available capacity
• Grounding system condition
• Location for inverter and AC disconnect

System Design Output

• String layout with shading losses modeled per string
• Inverter selection (string inverter vs. microinverters vs. DC optimizers)
• Wire routing and single-line electrical diagram

Week 2–4: Permitting

For a grid-tied installation you need:

1. <strong>Building permit</strong>: Structural drawings, roof plan, equipment specs
2. <strong>Electrical permit</strong>: Single-line diagram, NEC 690 compliance documentation
3. <strong>Utility interconnection application</strong>: Required before net metering activation (2–8 weeks review)

Many jurisdictions have streamlined solar permits for residential systems under 10 kW — your installer should know local requirements.

Installation Day

Morning — Mounting:

• Roof penetrations planned at rafter locations (never between rafters)
• Stanchions/lag bolts installed through roof deck into rafters
• Flashing installed under adjacent shingles and sealed
• Rails attached and leveled
• Panels lifted to roof, slid onto rails, clamped

Afternoon — Electrical:

• String wiring terminated into combiner box
• Conduit run from roof to inverter
• PV wire (USE-2 or PV wire, UV-rated) run through conduit
• Inverter mounted, AC disconnect installed
• PV system breaker installed in main panel
• System commissioned and test production run verified

Inspection

The building inspector verifies:

• Structural attachment meets permit drawings
• NEC 690 compliance
• Labels, placards, and disconnects properly located
• Rapid shutdown device installed (required by NEC 2017+ in most jurisdictions)
• Grounding and bonding correct

Permission to Operate (PTO)

After permit sign-off, your installer submits to the utility. The utility issues PTO — typically within 1–5 business days for standard residential installations.

Do not run grid-tied in grid-connected mode before receiving PTO — back-feeding an energized grid line is a lineworker safety hazard.

Net Metering: How You Get Credit

Once PTO is issued, your utility installs/activates a bidirectional meter and activates your net metering tariff. Excess solar production credits your bill. Net metering policies vary significantly:

• <strong>Retail rate NEM</strong>: Credits exports at full retail rate — most favorable
• <strong>NEM 3.0 (California)</strong>: Export rates tied to time-of-use avoided cost — batteries strongly recommended
• <strong>Avoided cost NEM</strong>: Credits at wholesale rate ($0.03–$0.06/kWh) — southeastern US

Always verify your utility's current NEM tariff before system design.

Monitoring

Set up email alerts for zero production on sunny days — the most common sign of a fault before you notice a bill increase. Most inverter apps show real-time power, daily/monthly/lifetime kWh, CO₂ offset, and system fault alerts.