A solar EPC business does not lose money on the panels — it loses money in the gaps. The survey engineer's numbers live in a spreadsheet, the design kW never quite matches what procurement ordered, the crew arrives before the inverter clears customs, and six months later nobody can find the signed net-metering application when the utility asks for it. ERPNext already gives you a strong spine for this — Project, Task, BOM, Material Request, Purchase Order, Stock Entry, Timesheet, Sales Invoice and Maintenance Schedule are all real, mature DocTypes. What ERPNext core does not have is any concept of a roof, a shading factor, a string layout, a subsidy milestone, a net-metering approval, or a commissioning test reading. So EPC teams bolt a parallel spreadsheet universe onto a perfectly good ERP, and the two drift apart within a quarter.

We build a proper Frappe app — its own repository, its own module, installed with bench get-app and bench --site <site> install-app — that adds the solar-specific layer and then wires it into the ERPNext documents you already use. New DocTypes cover the domain: Site Survey (roof or ground type, tilt, azimuth, usable area, shading loss factor, structure and cable-run notes, geotagged photos through the native File attachment system), Solar System Design (DC/AC capacity, module and inverter selection, string configuration, estimated annual yield), Solar Project (a linked extension of the ERPNext Project, carrying scheme type, sanction reference, connection voltage and commissioning date), Subsidy Application and Net Metering Application each with their own Frappe Workflow, and O&M Contract with a child table of covered assets and SLA response targets. An approved Solar System Design submits into a real ERPNext BOM and Sales Order, so procurement, stock, costing and accounting stay entirely native — no shadow inventory.

The automation lives where Frappe expects it. hooks.py doc_events fire on Sales Order.on_submit to create the Solar Project and expand an installation task tree from a configurable Project Template, and on Stock Entry.on_submit to record serial-numbered module and inverter dispatch against the site. scheduler_events (daily and cron entries) chase approaching subsidy deadlines, flag O&M Contract records nearing expiry, and open preventive Maintenance Visit documents at the visit frequency you configure. Client scripts handle field-facing arithmetic — live kW roll-up as modules are selected, string-count validation against inverter MPPT limits — while server-side validate logic enforces the rules that must not be bypassed by a REST call. Role profiles separate Survey Engineer, Design Engineer, Project Manager, Procurement, Site Supervisor and O&M Technician, with permission levels and User Permissions scoping technicians to their own territory. Everything is reachable over the Frappe REST API (/api/resource/Site Survey, /api/resource/Solar Project) plus a small set of @frappe.whitelist() methods for what a mobile crew client or an inverter-monitoring integration actually needs — pulling a task list, posting survey readings, pushing generation figures — so nobody has to hand-write SQL against the site database.

Delivery is build-to-order, and we are direct about what that means: this is not a Frappe Cloud Marketplace app you install this afternoon. It starts with a short scoping call, after which we write the DocType, workflow and integration specification against your real process — your subsidy scheme, your utility's document set, your commissioning checklist — and you sign off on that before a line of code is written. Typical delivery is one working week from confirmed scope. We build against Frappe/ERPNext v15 and v16, deploy to a staging site for UAT with your own survey and project data, then install on production with a documented rollback plan. You receive the full source repository, so the app is yours to run, fork or extend regardless of what happens to any vendor relationship.