Installation does not begin with bolting down modules. Where the sequence is not understood, two outcomes recur: the project stalls when a structural report is requested late, or the design has to be reworked because the grid application does not match the installed capacity. The sequence below avoids both.
Modules and mounting add a permanent load to the roof. Whether the existing structure can carry it — together with snow and wind loading — must be assessed by a structural engineer.
Where fixings penetrate the roof, every point is a potential leak. On flat roofs, ballasted systems can avoid penetrating the membrane altogether; the choice depends on roof type and load capacity.
The installed capacity must match the value declared in the grid application. For self-consumption systems, replacing the meter with a bi-directional one is part of the same process.
Without service walkways between the arrays, cleaning and fault work become difficult. These clearances are planned at layout stage; they cannot be created afterwards.
A quotation given without measurement loses either way: too low and the shortfall comes out of the contractor's margin; too high and the job goes elsewhere. No sound figure exists until module count, installed capacity and the bill of materials are derived from the roof's own geometry.
The preliminary design is also the input to the structural and grid steps: the load figure given to the engineer and the capacity declared in the application both come from it.
String lengths that fall outside the inverter's input window, cable runs made longer than necessary, and neglected earthing continuity come first.
Another is shading: a chimney or neighbouring building noticed only during installation will leave yield below expectations if the layout was never tested with a shading analysis at design stage.
Order matters: each step produces the input for the next. A skipped step usually means going back.
Typically a roof plan, structural information, consumption data and a preliminary design showing the installed capacity; the network operator then adds its own forms and approvals. Requirements vary by country and capacity — check the current list with your network operator.
The physical work on a mid-sized roof is usually a matter of days. What sets the overall timeline is not the installation but the administrative steps: connection approval and the meter change.
The load per square metre from the modules and mounting is calculated and compared with the existing structure's capacity. A structural engineer makes that assessment; the preliminary design supplies the load and layout information they need.
The roof belongs to the owner, so written consent is required. The investment's payback period should also be weighed against the remaining term of the lease.
Draw the roof and have module count, yield and cost in hand on day one. Runs in the browser.