This is the sequence a rooftop DIY installation actually follows, with the points where first-timers most often go wrong. It assumes you have already resolved the permit and the licensing question, and that a licensed electrician is handling the service-panel connection. Do not start buying equipment before both are settled.
Before anything: safety and the code edition
Two things settled first. Fall protection — harness, rated anchors, and a ladder secured properly — is not optional, and falls are the leading cause of serious injury in this work. And find out which NEC edition your jurisdiction enforces, because rapid-shutdown requirements changed between recent editions and designing to the wrong one means redoing the DC side.
Step 1: Layout and rafter location
Mark your array position respecting fire-access setbacks — many jurisdictions require clear pathways at the ridge and along edges, commonly around 3 feet, though this varies. Then locate rafters accurately. Attachments must land in structure, never in sheathing alone. A stud finder gets you close; a small pilot hole confirms. Getting this wrong is how arrays end up loose and roofs end up leaking.
Step 2: Flashing and attachments — the step that matters most
Each attachment is a penetration of the weather barrier. Done correctly on asphalt shingle, the flashing slides under the course above and over the course below, so water runs over the top of it. Sealant goes around the lag bolt beneath the flashing as a secondary barrier, not as the primary one.
Sealant is not flashing. A blob of roof caulk over a lag bolt will hold for a couple of years and then fail, and by the time you see a stain on the ceiling the sheathing has been wet for months. This single detail is the most common cause of DIY roof-solar regret. Tile and metal roofs need entirely different flashing systems — buy the one matched to your roof, not a generic kit.
Torque lag bolts to the racking manufacturer's spec. Overtightening strips the rafter; undertightening leaves the array to work loose under wind load.
Step 3: Rails and panel mounting
Rails go onto the attachments, levelled and squared. Panels clamp to the rails with mid-clamps between and end-clamps at the ends. Most racking systems bond the panel frames to the rails through the clamps as you go — check whether yours does, because if it does not you need separate bonding jumpers, and grounding is the most commonly failed inspection item.
Panels are awkward rather than heavy: a 400W module is roughly 21 square feet and acts like a sail. Two people, and never on a windy day.
Step 4: DC wiring, and the thing to respect
The array is live whenever light hits it. There is no breaker to switch off. Cover panels with an opaque tarp while wiring, work in low light, and check voltage with a multimeter before touching any connection. Never break a DC connection under load — DC arcs do not self-extinguish the way AC arcs do.
- Wire strings to your design, confirming series and parallel against the plan
- Verify cold-weather Voc stays within the inverter's maximum input — panel voltage rises as temperature falls
- Crimp MC4 connectors with the correct tool; a poor crimp is a future hot spot
- Secure all wiring off the roof surface; nothing rests on shingles where it will chafe
- Run conductors in conduit where required, sized for current and voltage drop
Step 5: Rapid shutdown
Recent NEC editions require module-level rapid shutdown on rooftop arrays, so firefighters can de-energise conductors on the roof. In practice this means either microinverters, DC optimisers, or module-level shutdown devices — a plain string inverter with no such equipment will not pass inspection on a roof under these editions. Confirm what your adopted edition requires before ordering the inverter, since this is one of the more expensive things to discover late.
Step 6: Inverter, disconnects and labelling
Mount the inverter per its manual — most need shade and clearance for airflow. Install DC and AC disconnects where your plan and inspector require them. Then label everything: disconnects, conductors, the point of interconnection, and the placard at the service equipment. Labelling is trivially easy to get right and a genuinely common reason for a failed first inspection.
Step 7: Electrician, inspection, interconnection
Your electrician makes the service-panel connection and any main-breaker derate. Then the inspection, then the utility interconnection application, and only after Permission to Operate may the system run. Do not energise before PTO. What inspectors look at is covered in the inspection guide, and the utility process in the interconnection guide.
This is an overview of the normal sequence, not a substitute for your equipment manuals, your adopted code, or your inspector. Where any of those disagree with this article, they are right.