The Solar Installation Process, Step by Step

The physical work is often the shortest part. Here's the whole sequence, and where the delays actually come from.

Installation, step by step

The panels go up in a couple of days. Everything else is paperwork — and the last step, permission to operate, is the one that surprises people: the system is physically complete, on the roof, and legally must stay switched off until the utility says otherwise.

What happens during a solar site assessment?

A competent installer visits and evaluates:

• Roof condition, age, material and structure — see roof suitability for solar
• Orientation and tilt of each usable plane
• Shading, with a site-specific analysis modelled across the year — see how shading affects solar panels
• Usable area after setbacks and obstructions
• The electrical panel — capacity, spare spaces, condition
• Where equipment will go and how conductors will route

Be wary of a firm quote produced without a site visit. Satellite imagery misses roof condition, structure and a lot of shading.

Stage 2: Design and proposal

You should receive:

• System size, panel and inverter models and quantities
• A layout showing panel placement on each roof plane
• An estimated annual production figure — location-specific, orientation-specific, with a stated derate. See peak sun hours explained.
• Monthly production, not just an annual total
• Total cost, itemized
• Warranty terms for panels, inverter, racking and workmanship separately

Compare proposals on estimated annual production per total dollar, not on panel brand or system size. See choosing a solar installer and solar system sizing mistakes.

Stage 3: Contract and engineering

After signing, the installer produces stamped engineering drawings — electrical single-line diagrams, structural details, mounting layout — for the permit application.

Some jurisdictions require a structural engineer's review, particularly for older roofs.

Stage 4: Permitting and interconnection application

Two parallel processes, and they're usually what sets the timeline:

The building permit, from your local authority, covering electrical and structural work.

The interconnection application, to your utility, seeking approval to connect a generating system to their grid.

Both timelines vary enormously by jurisdiction and utility — from quick to lengthy. Your installer handles the paperwork, but they don't control the queue.

Ask for a realistic local estimate rather than a best case. See solar permits and interconnection.

What happens on solar installation day?

The short part. On a typical home, often one to a few days.

Roughly:

1. Mounts installed — located on rafters, flashed into the roofing. This is the step that determines whether your roof leaks in year eight. See solar racking and mounting systems.
2. Rails or rail-less hardware attached
3. Panels mounted and clamped
4. Module-level electronics installed, if used
5. Conductors run from array to inverter location, in conduit
6. Inverter and disconnects mounted
7. Electrical connection made at the panel — this is when your power is off briefly
8. Labeling and signage applied
9. Monitoring configured

You'll typically need to provide access to the panel and possibly the attic.

Stage 6: Inspection

A local inspector reviews the installation — mounting, flashing, conductor sizing, grounding and bonding, disconnects, labeling, and compliance with the permitted drawings.

If corrections are needed, the installer addresses them and re-inspection follows, which adds time.

What is permission to operate?

The final gate. After inspection, the utility issues permission to operate (PTO) — formal authorization to energize and connect.

You cannot legally switch on before this. Doing so can breach your interconnection agreement.

PTO timing is largely outside your installer's control and is frequently the longest single wait in the project. It's also the stage where owners get frustrated, because the system is physically complete and sitting idle.

The utility may also swap your meter for a bidirectional one at this point.

Stage 8: Commissioning and handover

Once authorized:

• The system is energized and verified
• Monitoring is confirmed working, and you're shown how to read it
• Documentation handover — warranties, manuals, permit records, the as-built layout, monitoring credentials

Keep all of it. It matters for warranty claims and at resale. See solar and home resale value.

What delays a solar installation?

• Permit backlogs — seasonal and jurisdictional
• Utility interconnection queues — often the longest wait
• Structural review requirements
• Equipment lead times
• Failed inspection requiring corrections and re-inspection
• Weather, for roof work
• HOA approval, where applicable — start this early
• Panel upgrades discovered necessary, adding a separate scope and utility coordination

That last one is worth pre-empting: if your electrical panel may constrain the system, find out during the assessment rather than mid-project. See Electrical panel upgrade and check with the home electrical load calculator.

Questions worth asking up front

• What's the realistic timeline in this jurisdiction, including PTO?
• Who handles the permit and interconnection paperwork?
• Will a structural review be required?
• Is any panel work needed, and is it in the quote?
• What happens if the system underperforms the estimate?
• How long is the workmanship warranty, and does it cover roof leaks?

After switch-on

• Check monitoring in the first weeks and confirm every panel is reporting
• Compare early production against the monthly estimate, allowing for weather
• Understand your new bill — see net metering explained
• Note the inverter warranty expiry for your records

See solar panel monitoring explained and why is my solar production low.

The bottom line

Site assessment, design, permitting, installation, inspection, permission to operate, commissioning — and the physical install is usually the shortest stage. Permitting and utility interconnection set the calendar, and permission to operate is a hard gate you can't switch on before. Ask for realistic local timelines rather than best cases, resolve any panel-capacity question during assessment, and keep every document at handover.

Size your system with the solar panels needed calculator, model economics with the solar panel payback calculator, or read choosing a solar installer.