From first site visit to a system that is generating, in order, with honest timings and the three things that most often go wrong.
Useful whether you are considering the career, considering a system for your own roof, or about to be on your first crew. The physical work is a fraction of the elapsed time, which is the first thing that surprises people.
Someone measures the roof, checks orientation and tilt, assesses shading across the year rather than at that moment, looks at the roof's structure and remaining life, inspects the electrical service and panel capacity, and decides where the inverter and disconnects will physically live. They also work out how a crew gets up there safely.
Most of a job's profitability is decided here. A survey that misses an undersized service, a roof with five years left, or a chimney shadow that only matters in November produces a quote that loses money.
Array layout, string configuration, inverter selection, conductor sizing, and a yield estimate with realistic losses. Then a price. For a commercial roof, structural sign-off may be needed before anyone can commit to a layout.
The longest part, and none of it is on a roof. An electrical permit or notification. A net metering or interconnection application to the local utility, with their own requirements and timeline. Possibly a structural review or a municipal permit. Nothing can be installed until this is through, and telling a customer "two days" when the honest answer is "two days of work inside two months of process" is how installers get bad reviews they have earned.
Attachments located on structure, not on sheathing. Flashing installed so the roof still works. Rails aligned, levelled and torqued to specification. On a flat commercial roof, ballasted or mechanically attached racking instead, with wind uplift calculated rather than guessed.
This is the step whose mistakes appear last. A penetration that is not properly flashed will leak, and it will leak long after everyone has been paid.
Modules placed, clamped to torque, and strung in the configuration the design specified — not in whatever order is convenient, because string length was calculated for a reason. Conductors routed, secured off the roof surface, and protected from abrasion and UV. Polarity checked before anything is energised. Rapid shutdown or module-level devices where required.
Inverter mounted where it can be serviced and will not cook. DC and AC terminations. Disconnects. Overcurrent protection and the connection into the building's panel. Labelling — which is not bureaucracy: the labels tell the next person, possibly a firefighter, that there is a DC source on the roof that cannot be switched off.
The authority having jurisdiction inspects before the system may operate. A clean job with correct labelling and accessible documentation passes. An untidy one does not, and a second visit costs more than doing it properly cost.
Measure open-circuit voltage per string and compare it to what the design predicted — a disagreement here means a wiring error or a wrong module count, and finding it now is far cheaper than finding it in June. Operating current, insulation resistance, polarity. Then the inverter is energised and watched through start-up. Finally the handover: documentation, monitoring access, and an explanation of what the owner should expect to see and when.
All three are avoidable, all three are expensive, and none of them is caused by the part of the work that looks skilled.
What installation training covers, module by module → · How panels work, if you want the physics first →
The physical work is typically two to three days for a house. The elapsed time from signature to generating is usually weeks to months, because permits and the utility application are the long part.
The electrical scope of a grid-tied system is regulated, and in Ontario must be performed and filed appropriately. Off-grid rules differ. Check locally before assuming.
String length that does not account for cold temperatures, and roof penetrations that are not properly flashed. One kills an inverter, the other a ceiling.
Because measuring string voltage against the design prediction catches wiring errors on the day instead of in the first cold snap.
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