Rooftop solar prices vary because projects vary. Two systems with the same rated capacity can have different module counts, inverter designs, structure heights, cable runs, roof fixing methods, protection scope, access needs, approval responsibilities, warranties, and service commitments.
Compare total scope, not just total price or price per kilowatt. The most useful quotation names exact equipment, quantities, technical specifications, inclusions, exclusions, taxes, payment milestones, warranties, and handover documents.
1. Solar modules
Module technology, rated power, efficiency, physical dimensions, product warranty, performance warranty, manufacturer support, and supply traceability affect cost. A higher-watt module does not automatically create a better system; it may simply change module count and layout.
2. Inverter and electrical design
Inverter type, capacity, phase, number of MPPTs, monitoring, protection features, grid compatibility, warranty, and service network matter. The design also includes DC and AC cables, connectors, isolators, surge protection, distribution boxes, conduits, labels, earthing, and lightning protection where required.
3. Mounting structure
Structure cost changes with roof type, height, orientation, wind design, steel or aluminium specification, coating, fasteners, foundations, walkways, and waterproofing method. A higher elevated structure can provide useful roof access but demands more engineering, material, and installation work.
4. Roof and site conditions
- Sheet roof versus reinforced concrete terrace.
- Weak or damaged roof requiring remedial work.
- Difficult material lifting or restricted access.
- Long cable route between array, inverter, and interconnection point.
- Multiple roof levels or scattered module groups.
- Shadow mitigation or optimizer requirements.
- Work-hour restrictions, permits, or safety infrastructure.
5. Project size and complexity
Larger projects may distribute some fixed costs over more capacity, but they can also require more detailed engineering, dedicated panels, transformer or protection studies, shutdown coordination, structural certification, safety planning, and project management.
6. Batteries and backup
Adding backup changes both equipment and engineering. Battery chemistry, usable energy, power capability, cycle life, enclosure, thermal conditions, protection, critical-load wiring, and replacement planning should be specified. A quote that says only “lithium battery” is incomplete.
7. Approval and metering scope
Clarify whether portal work, technical applications, meter coordination, testing, documentation, and follow-up are included. Government or utility charges should be shown separately where they cannot be fixed by the installer.
8. Warranty and service
A warranty is valuable only when the customer knows who receives the complaint, who visits the site, whether labour and travel are covered, and how manufacturer claims are handled. Remote monitoring, preventive maintenance, response commitments, and local service capacity can justify a difference in price.
Ask for an itemized commercial offer
| Cost area | What the quotation should identify |
|---|---|
| Equipment | Make, model, capacity, quantity, and warranty. |
| Structure | Material, section, coating, height, fixing method, and design basis. |
| Electrical | Cables, protection, earthing, boxes, monitoring, and interconnection. |
| Services | Survey, design, installation, approvals, commissioning, and training. |
| Commercial | GST type, payment milestones, validity, exclusions, and change-order method. |
A final project decision should also consider expected generation assumptions, energy use, financing cost, maintenance, and downtime risk. A cheap incomplete system can be more expensive over its life than a complete, serviceable one.
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